Phytomedicine Plus 1 (2021) 100036 Contents lists available at ScienceDirect Phytomedicine Plus journal homepage: www.elsevier.com/locate/phyplu Heliotropium; a genus rich in pyrrolizidine alkaloids: A systematic review following its phytochemistry and pharmacology Marwa A.A. Fayed Department of Pharmacognosy, Faculty of Pharmacy, University of Sadat City, Sadat 32897, Egypt a r t i c l e Keywords: Heliotropium Boraginaceae Pyrrolizidine alkaloids Quercetin Phytochemistry Pharmacology i n f o a b s t r a c t Introduction: A huge number of plants have remedial and therapeutic prospects throughout the world and are used in the treatment of diverse diseases. Heliotropium is a large genus of family Boraginaceae which widely distributed in tropical and temperate regions of hemispheres. The purpose of this review is to recapitulate the phytochemistry and pharmacological activities of the Heliotropium species to unveil future research prospects. Methods: Published data in this review were all gathered from the online bibliographical databases: PubMed, Elsevier, Scopus, Google Scholar and Web of Science. Results: The plants of the Heliotropium genus in the history of traditional drugs provide remedies for gout, inflammation, skin disorders, menstrual dysfunction, rheumatism, and noxious bites. The active biochemical constituents extracted from the Heliotropium species comprise pyrrolizidine alkaloids, flavonoids, and terpenoids. Significant biological activities viz. antimicrobial, antiviral, antitumor, anti-inflammatory, cytotoxicity, phytotoxicity, and wound healing were revealed by an enormous number of extracts and biochemically active constituents of various species of the Heliotropium genus. Conclusion: Phytomedicines are now an important and beneficial zone of the recommended treatment and have high potentials in many countries. Although this clear evidence that plants of the Heliotropium genus have several medicinal importance in the treatment of diverse diseases. The medicinal use of these plants as phytopharmaceuticals would depend on the production of the required systematic procedures necessary to standardize the various bioactive secondary metabolites in such herbal formulations. Therefore, we conclude that in the coming period, plants of the Heliotropium genus would become an acceptable source of indigenous medicines. Introduction Constituents that derive from plants, animals, marine, and microbial sources are natural products. The components identified and extracted from plants have been utilized for several years as a lead for several treatments. About 40–45% of the drugs commonly used are primarily extracted from natural sources. As a result of their wide availability in the environment, natural products also show an essential role in the discovery of novel therapeutic agents, contributing to the identification of biochemically active compounds that allow the advancement of novel medicinal agents (Calixto et al., 1998). The method which is required in clarifying complex molecular and cellular mechanisms of action is also involved in many pathogenic and biological process. Because of the growing interest in the use of pharmaceuticals in recent years, natural substances have been the fundamental source of complementary or substitute therapeutic drugs used in the healing of numerous diseases (Ghori et al., 2016). From ancient eras, medicinal plants are available to human beings as a source of remedy. Medicinal plants and their significance of healing ailments are used widely all over the world for several diseases. In the 19th century, more than 25% of medicines used in welldeveloped countries are of plant source because of enhancements in the arena of pharmaceutical science, medicinal chemistry, and about 120 plant-derived compounds are used in modern medicine systems worldwide (Sharma et al., 2009). The family Boraginaceae consists of hundreds of genera and about two thousand species. The plants of this family are far and wide dispersed in tropical and temperate regions, especially the Mediterranean. Heliotropium, Arnebia, Martensia, Cordia, and Trichodesma are the main genera of the Boraginaceae family. Heliotropium is a large genus of the Boraginaceae family, consisting of about 250–300 species worldwide. The name “heliotrope” originates from the ancient ideas that these plants turned their leaves towards the sun. ‘Helios’ meaning in Greek languages is ‘sun,’ and the ‘tropium’ word comes from another Greek word ‘tropein’ and the meaning of this word is ‘to turn’ (Selvi and Abbreviations. DPPH, 1,1-diphenyl-2-picrylhydrazyl; EC, estimation concentration; H, Heliotropium; LD, Lethal dose; MICs, minimal inhibitory concentrations. E-mail address: marwa.fayed@fop.usc.edu.eg https://doi.org/10.1016/j.phyplu.2021.100036 Received 17 December 2020; Received in revised form 23 January 2021; Accepted 28 January 2021 2667-0313/© 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 Bigazzi, 2001). Heliotropium consists of suffruticose perennial and annual herbs. They are simply identified by their partial inflorescences of scorpioid cymes and by the morphology of the greatly modified stigmatic head in the flower (Riedl, 1967). Some of the taxa of this genus are H. indicum L., H. ovalifolium Forssk., H. bacciferum Forssk., H. gillianum R., H. sclerocarpum Phil., H. baluchistanicum K., H. biannulatum B., H. europium L., H. strigosum Willd., H.glutinosum Phil., H. eichwaldi Steud., H. subulatum Hochst., H. sinuatum Miers., and H. foertherianum D. (Akhani and Förther, 1994). Pyrrolizidine alkaloids, flavonoids, terpenoids, naphthoquinones, and phenols comprise various biochemical active constituents extracted and categorized from plant species of the family Boraginaceae (Pandey et al., 1996). Economically, some Heliotropium species are of local importance in folk medicine or traditional practice; while others (e.g. H. strigosum, H. europaeum, and H. zeylanicum) show antibacterial and antifungal activities (Paulraj et al., 2013). Few species are known to have toxic effects caused by the presence of hepatotoxic pyrrolizidine alkaloids which are shown to be responsible for many liver diseases. H. ovalifolium was found to possess Helifoline and Retronecine as major alkaloids both are hepatotoxic pyrrolizidine alkaloids (Mohanraj et al., 1981). Previously, significant biological and pharmacological activities have been studied from various parts of different plant species of Heliotropium. The biochemically active compound of Heliotropium species exhibits anti-bacterial, anti-fungal, anti-viral, anti-tumor, antioxidant, anti-inflammatory, antiplatelet, wound healing, cardiotonic, contraceptive, and prostaglandin properties (Sharma et al., 2009; Noumedem et 2013). We conducted a systematic review of the literature to recapitulate the currently reported biochemically active constituents and pharmacological activities of Heliotropium species. have been used in different traditional and folklore systems of medicine for healing various sicknesses. Different parts of the plant viz. leaves, roots, flowers, seeds, and the whole plant are used to cure the various diseases (Dash and Abdullah, 2013). The Heliotropium species plants in the history of folk medicines provide cures for gout, inflammation, skin disorders, menstrual dysfunction, rheumatism, and noxious bites. H. indicum is used to cure fever, stomachache, skin diseases, diarrhea, menstrual disorder, nervous disorders, and poison bites (Kumar et al., 2007). H. aegyptiacum leaves were boiled with coconut oil to kill dandruff (Giday et al., 2003). H. strigosumm is used as a laxative, diuretic, and helps to cure sore eyes, gum boils (Modak et al., 2003). The whole plant of H. amplexicaule is used to reduce the temperature of the body and to get relief from the Common cold (Schmelzer and Gurib-Fakim, 2008). H. europaeum, is a species rich in essential oil, that has been used in the Iranian traditional medicine as antipyretic, cholagogue, emmenagogue, cardiotonic, and anthelmintic, besides the treatment of headache and gout, also it has been used externally for healing wounds, and treatment of warts (Zargari A. 1992). There is a wide range of significance of ethnopharmacological flora, this systemic review was summarized and enlisted in the tabular form (Table 1) about the different species of the genus Heliotropium and its traditional uses. Phytochemical studies of the genus heliotropium Till now, phytochemical evaluations have discovered numerous compounds that have been extracted and identified from the different species of Heliotropium. Heliotropium species are phytochemically bioactive and have remarkable healing effects. Several classes of organic compounds viz. flavonoids, pyrrolizidine alkaloids, terpenoids, and quinones are very plentifully present in the Heliotropium genus. Morphological and anatomical studies of genus heliotropium Pyrrolizidine alkaloids Pyrrolizidine alkaloids exist predominantly as esters that are followed by distinctive mono or dibasic acids known as necic acids. Heliotropium species are very rich in pyrrolizidine alkaloids (Fig. 1). Abundant pyrrolizidine alkaloids (as shown in Fig. 1) have been isolated in these plants by many researchers. The alkaloids reported in H. indicum that the whole plant include indicine, heliotrine, indicinine, indicine-Noxide, lasiocarpine, 12-acetyl indicine, trachelan-thamide, retronecine with traces of lindelofidine and supinidine (Duke, 1994; Lin and Kan, 1990; Wiart, 2006; Mattocks, 1967a, 1967b; Mattocks et al., 1961). The aerial parts of H. indicum comprise echinatine, supinine, heleurine, heliotrine, lasiocarpine-N-oxide, lasiocarpine, indicine, and indicine-N-oxide (Lin and Kan, 1990; Wiart, 2006; Mattocks, 1967a, 1967b; Mattocks et al., 1961; Dutta et al., 1987). Existence of cynoglossine, heliotrine, europine-N-oxide, heleurine-N-Oxide, heleotrine-NOxide, and heliotridine-N-Oxide have been identified from the seeds (Kugelman et al., 1976; Birecka et al., 1983). Other alkaloids viz. homo spermidine, spermidine, spermine, and putrescine have been identified in the leaves of H. indicum [46]. Helindicine, a novel pyrrolizidine alkaloid accompanied by the known lycopsamine were extracted from the H. indicum roots. This is the first report of a lactone pyrrolizidine alkaloid in the genus Heliotropium. Lycopsamine and helindicine were evaluated for antioxidant activity and exhibited moderate activity (Andhiwal et al., 1985). Subulacine, supinidine, retronecine, lindelofidine, and trachelanthamidine were biochemically active compounds obtained from different parts of H. angiospermums (Birecka et al., 1983). On the other hand, H. supinum L. comprise of different active constituents viz. Supinine, heliotrine, echinatine, heliosupine, lasiocarpine (Mattocks et al., 1986). A systemic morphological and anatomical studies on stems and leaves of diverse species of genus Heliotropium viz. H. strigosum, H. longiflorum DC., H. arbainense, H. lasiocarpum F., H. petrocarpum DC., H. jizanense O., and H. zeylanicum Burm. was described by illustrating the most significant characters including stem anatomy, stomata, hairs, and pollen grains (Kasem, 2015). The study of leaves stomata of H. indicum was also documented (Dattagupta and Datta, 1977). The anatomy of four different Heliotropium species leaves namely H. strigosum, H. subulatum, H. digynum, H. curassavicum were reported (Alwahibi and Bukhary, 2013). Moreover, the differentiation of anatomical characteristics of H. ovalifolium, H. bacciferum, H. strigosum, H. sudanicum A., H. supinum was also recorded (Hoyam and Maha, 2012). The morphology of the epidermal layer of H. rigidum DC., H. dasycarpum, and H. europaeum was studied (Dasti et al., 2003). One researcher reported the morphology of pollen of H. bacciferum (El-Ghazaly, 1995). In brief, researchers concentrated primarily on several of the leading morphological and anatomical features of the leaves and stems of Heliotropium species during these important studies. These principal characteristics consist of leaf venation, measurements of leaves including width (cm), length (cm), and shape of leaves, measurements of inflorescence, different characteristics of stomata, primarily kinds and numbers of stomata, width (mm) and length (mm) of stomata, types and pollen grains measurements, and various analyses of epidermal membranes, pith and cortex cells. Traditional/Folk medicinal uses In modern eras, more than 80% of the ecosphere’s people depend on the folk medication system. Because of rebellions in traditional theory, awareness of traditional health care programs is frequently demoralized around the world (Hussain et al., 2008). About 90% of natural products are consumed by the local folks of the region in which the plants exist (Baquar, 1989). Native and folk knowledge of medicinal plants remain to exist globally (Haider and Zhong, 2014). Heliotropium species Flavonoids Within this genus, flavonoids (Fig. 2) are the mostly common class of bioactive secondary metabolites. Flavonoids are the mainly occurring phenols formed of a phenylpropane unit and three acetate units (Evans, 2009). Flavonols and Flavones and their glycosides are 2 M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 Fig. 1. Some of the Pyrrolizidine alkaloids from the genus Heliotropium. the most common constituents are found as flavonoids in the genus Heliotropium. Different scientists in many research surveys have characterized and identified various flavonoids (Fig. 2) viz. 5,4′-dihydroxy7-methoxyflavanone, 4′-acetyl-5‑hydroxy −7-methoxyflavanone, 4‑methoxy-3-[(2)−7′-methyl-3′-hydroxymethyl-2′,6′-octadienyl] phenol, 5,3′-dihydroxy-7,4′-dimethoxyflavanone, 7-O-methyleriodictiol, 3-O-methylgalangin, filifolinol, filifolinyl senecionate, naringenin, filifolinoic acid, filifolinone, 3-oxo-2-arylbenzofuran, dihydroquercetine, quercetin, etc. (Modak et al., 2009a, 2009b,; Modak et al., 2007, 2010; Goyal and Sharma, 2014 and Mughal, 2009). Essential oil Several Heliotropium species were rich in essential oil which possessed important pharmacological effects in addition to their fragrance and aroma. Heliotropium arborescens is one of the species which is characterized by its fragrant flower. It has a pleasant odor that resembles vanilla with a caramel mixture. The major constituents identified in the essential oil of Heliotropium arborescens; benzaldehyde, anisaldehyde and benzyl acetate in addition to 3,4-methylenedioxybenzaldehyde which has been called ’heliotropin (Hisano et al., 1995). H. europaeum main essential oil constituents were Phytol (28.7%), cis-Linoleic acid methyl ester (7.3%), Geranyl acetone (6.3%), (E)-𝛽-Ionone (4.8%), and Phytol acetate (4.3%) (Saeedi and Morteza-Semnani, 2009). The essential oil of Heliotropium indicum has been reported to contain a high amount of aldehydes about (52.8%) which the major ones were phenylacetaldehyde (22.2%), (E)−2-nonenal (8.3%) and (E, Z)−2-nonadienal (6.1%), with a significant quantity of hexahydrofarnesylacetone (8.4%) (Ogunbinu et al., 2009). Heliotropium hirsitutissimum essential oil rich in 1-hexadecanol, tetracosane acid, butyl 2-methylpropyl ester, 4,4′-(1methylethylidene)bis-(CAS) 2,2-bis(p-hydroxyphenyl)propane, ethanol, 2–2′-(1–2-ethanediol bis(oxy))bis-(CAS)triethylene glycol, octadecanoic acid (stearic acid), 2‑hydroxy-1-(hydroxymethyl) ethyl ester (CAS) and 2-Monostearin (Demiray et al., 2013). Heliotropium stenophyllum essential oil constituents reported are junenol (19.08%), longiborneol (9.34%); (E, Z)-geranyl linalool (6.81%); selina-3,11‑dien-6-𝛼-ol (6.70%); 𝛼-cedrene epoxide (6.60%); heliofolen-12-al D (6.23%) and 𝛽‑epi-bisabolol (4.83%) (Urzúa et al., 2013). Terpenoids & quinones Triterpenoids are compounds containing about 30 atoms of carbon and are present as glycosides or esters. Apart from alkaloids and flavonoids, several triterpenes and steroids comprising 𝛽-sitosterol, 𝛽amyrin acetate, 𝛽-amyrin, friedelan-𝛽-ol, stigmasterol, cycloartenone, epifriedenyl acetate, friedelin (Fig. 3) have been reported from the whole plant (Singh and Dubey, 2001; Jain et al., 2001). The existence of estradiol has been studied in the roots (Birecka et al., 1984). Quinones are the member of cyclic organic compound which is derived from the aromatic compound and rarely found in some of the Heliotropium genus. Two new benzoquinones, heliotropinones A and B, have been extracted from the aerial parts of Heliotropium ovalifolium (Fig. 3) (Guntern et al., 2001). The bioactive compounds isolated from different species of Heliotropium are listed in Tables 2. 3 M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 Table 1 Traditional/Folk uses of different plants of Heliotropium genus in ethno-pharmacological studies. No. 1 2 3 4 5 6 7 8 9 10 Part of the plant References used Insect stings, insect bites and skin rashes Leaves (Muthul et al., 2006) Diuretic Whole plant (Dattagupta et al., 1977) Gonorrhea Whole plant (Wiart, 2006) Rheumatism Leaves (Nagaraju and Rao, 1990) Cleaning of ulcers, eye lotion, Whole plant (Schmelzer et al., 2008) Whooping cough in infant Leaves, roots (Anderson and Coee, 1996) H. aegyptiacum L. Dandruff Leaves (Giday et al., 2003) scorpion stings and snake bites Roots (Thulin, 1993) H. supinum L. Tumors Whole plant (Schmelzer et al., 2008) H. europaeum L. Cattle wounds, Acne Whole plant (Qureshi and Bhatti, 2008) antipyretic, cholagogue, emmenagogue, cardiotonic, anthelmintic, headache, gout, (Zargari A. 1992) externally for healing wounds, and treatment of warts Leaves (Schmelzer et al., 2008) H. ramosissimum Lehm. Burns H. strigosumm Willd. Laxative, diuretic, gum boils, and sore eyes Leaves (Roeder and Wiedenfeld, 2009) Breast abscesses Whole plant (Neuwinger, 2000) H. amplexicaule L. Fever and cough Whole plant (Schmelzer et al., 2008) Leaves (Shafi et al., 2001) H. eichwaldi Steud. Ear pain H. steudneri Verdc. Squeezed over bruises Whole plant (Dattagupta et al., 1977) Cuts or wounds to stop bleeding and to avert infection Leaves (Roeder and Wiedenfeld, 2009) H. dasycarpum Ledeb. Eye infections Leaves (Tareen et al., 2010) Heliotropium species H. indicum L. Traditional uses of different Heliotropium Species Pharmacological activities of genus heliotropium Heliotropium species have been used for thousands of years in the treatment of fever, cough, eye infection, stomach pain, laxatives, diuretics, gonorrhea, rheumatism, ulcer, skin rashes, snake bites, etc. Different Heliotropium species extracts have been tested in different animal models for prospective biological activity and have been reported to have substantial antimicrobial, antifungal, antiviral, antifertility, anti- inflammatory, histo-gastro-protective, anti-cataract, anti-tumor, analgesic, and wound healing properties. The following sections mainly describe the pharmacological effects of crude extracts and isolated compounds from the genus Heliotropium. Fig. 3. Some Terpenoids & Quinones from the genus Heliotropium. 4 M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 Table 2 Main active constituents isolated from different species of the genus Heliotropium. No. 1 Class Flavonoids Species Bioactive compounds H. taltalense Phil. 7-O-methyleriodictiol, 3-O-methylgalangin, filifolinol, filifolinyl senecionate, naringenin H. glutinosum Phil. Pyrrolizidine alkaloids 2 H. filifolium Miers. H. sclerocarpum Phil. H. strigosum Willd. H. indicum L. H. angiospermum Murr. H. bracteatum R. Terpenoids Quinones H. ovalifolium Forssk H. steudneri Verdc. H. strigosum Willd. H. acutifolium Kir. H. marifolium Koen. H. ovalifolium Forssk. Dihydroquercetine, quercetin Lycopsamine, heliotrine, heleurine, echinatine, indicine, acetylindicine, supinidine, helindicine, indicinine, lindelofidine, lasiocarpine, rinderine, supinine, retronecine, trachelanthamine Supinidine, subulacine, retronecine, lindelofidine, trachelanthamidine (Mughal et al., 2009) (Catalfamo et al., 1982; Souza et al., 2005) Retronecine, helibractinecine, helibracteatine, helibracteatinine, (Lakshmanan and Shanmugasundaram, 1994) (Hartmann et al., 1995) (Birecka et al., 1983) Supinine, echinatine, heliosupine, lasiocarpine, heliotrine Incanine, Heliotrine H. ellipticum Ledeb. 4 (Modak et al., 2010) (Goyal and Sharma, 2014) Indicine H. amplexicaule Vahl. H. supinum L. H. olgae B. 3 5,4′-dihydroxy-7-methoxyflavanone, 4′-acetyl-5-hydroxy −7-methoxyflavanone, 4‑methoxy-3-[(2)−7′-methyl-3′-hydroxymethyl-2′,6′-octadienyl] phenol, 5,3′-dihydroxy-7,4′-dimethoxyflavanone Filifolinone, filifolinol, filifolinyl senecionate, filifolinoic acid 3-oxo-2-arylbenzofuran, filifolinol, naringenin References (Modak et al., 2009a, 2009b,) (Modak et al., 2007) (Mattocks et al., 1986) (Kiyamitdinova et al., 1967) (Mohanrajet al., 1981) Heliofoline, retronecine Lycopsamine Strigosine, trachelanthamidine Heliotrine 𝛽-sitosterol, 𝛽-amyrin acetate, 𝛽-amyrin, friedelan-𝛽-ol, stigmasterol, cycloartenone, epifriedenyl acetate, friedelin 𝛽-sitosterol, 𝛽-amyrin, 𝛽-amyrin acetate, friedelan-𝛽-ol, stigmasterol, cycloartenone, friedelin Heliotropinones A & B (Mattocks et al., 1986) (Mattockset al., 1964) (Akramov et al., 1968) (Singh et al., 2001) (Jain et al., 2001) (Guntern et al., 2001) Table 3 Pharmacological activities of extracts obtained from different Heliotropium sp. No. 1 2 3 4 5 6 7 8 9 10 Heliotropium species H. ellipticum Ledeb. Extract obtained from Heliotropium species Ethanolic extract isolated from entire plant Pharmacological activities References Antibacterial Antifungal H. glutinosum Phil. H. sclerocarpum Phil. H. ovalifolium Forssk. H. filifolium Miers. H. subulatum Hochst. Dichloromethane isolate from fresh plant Dichloromethane extract from fresh plant Antioxidant Antiviral (Jain et al., 2001; Jainet al., 1987) (Modaket al., 2007) (Modaket al., B 2009) Petroleum ether isolate of aerial parts Anti-inflammatory (Kulkarniet al., 2008) Dichloromethane extract from fresh plant Ethanolic isolate of aerial parts (Valenzuela et al., 2013) (Singh et al., 2002a, 2002b; 78] Dichloromethane extract from cuticle Ethanolic extract from aerial parts Dichloromethane extract obtained from fresh plant Immunostimulant Antibacterial, Antifungal, Antiviral, Antineoplastic, cytotoxicity Antibacterial Anti-feedant Antioxidant (Urzúa et al., 2008) (Reina et al., 1997) (Modak et al., 2009a, 2009b) Ethanolic extract isolated from entire plant Antibacterial Antifungal (Singh et al., 2001) H. filifolium Miers. H. floridum A. H. sclerocarpum Phil. H. marifolium Koen. thracis and S. aureus. The chloroform fraction maintains optimum activity against E. coli between these two fractions, with a reported inhibition zone is 12.61±0.361 (Singh et al., 2002a, 2002b). The methanolic extract of aerial parts of H. indicum has wide-range spectrum of antibacterial activity against E. coli, S. aureus, S. pneumonia, S. typhi, S. pyogenes, C. ulcerans, and K. pneumonia with the zones of inhibition 28, 32, 0, 30, 35, 0, 27 mm demonstrated for these bacteria (Oluwatoyin et al., 2011). Methanolic extract of the leaf of H. indicum was assessed for its anti-bacterial activity against five isolates of bacteria consist of 1-gram positive bacteria, S. aureus and four gram-negative bacteria viz. E. coli, P. aeruginosa, P. mirabilis, and Klebsiella species, at different concentrations of 6.25, 12.5, 25, 50, 100 and 200 mg/ml of extraction of plant respectively. Both Klebsiella species and S. aureus were inhibited at 50, 100 and 200 mg/ml with MIC of 3 mg/ml, whereas P. mirabilis and P. aeruginosa were inhibited at 100 mg/ml and 200 mg/ml with MIC of 10 mg/ml and E. coli was inhibited only at 200 mg/ml concentration with MIC of Antibacterial activity Antibacterial activity of the methanolic isolate of the entire plant of H. strigosum exhibited different inhibition zones which are produced by crude extract, chloroform fraction, ethyl acetate fraction, n-hexane fraction, aqueous fraction, and standard doxycycline (30 μg). All these fractions are active against S. epidermidis with the minimum inhibitory concentrations (MICs) of 8, 8, 6, 6, 8 mg/ml but no fraction exhibited any activity against E. coli. The activity against methicillin-resistant S. aureus was only exhibited by the fraction of ethyl acetate with the inhibition zone documented is 8 mm. Other fractions and crude isolate did not exhibit any antibacterial activity against methicillin resistant S. aureus. The standard fraction of doxycycline exhibited activity against all bacteria used in the bioassay (Hussain et al., 2010). In addition, from the ethanolic extraction of the aerial parts of H. subulatum two fractions such as chloroform and n-hexane fraction experienced the substantial activity against bacteria such as E. coli, S. pneumoniae, B. subtilis, B. an5 M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 entire plant, including H. indium roots has been tested against certain fungi such as A. Niger, R. oryzae, and A. Wentii. At a concentration of 100 𝜇g/ml, the extract exhibited considerable activity with the inhibition area noted against A. niger, R. oryzae, and A. Wentii, compared to standard fluconazole, is 8.00, 8.00, 9.00 mm (Rao et al., 2002). Antioxidant activity The subsequent sub-fractions and crude extract of entire plant of H. strigosum were analysed for antioxidant activity by using 1,1-diphenyl2-picrylhydrazyl scavenging assay (DPPH). The n-hexane fraction of the methanolic isolate showed strong antioxidant activity with an EC50 value of 35.53 𝜇g/ml, while the ethyl acetate fraction also showed significant antioxidant activity with an EC50 value of 30.34 𝜇g/ml. The aqueous fraction also showed high antioxidant activity and had an EC50 value of 20.51 𝜇g/ml. There was no antioxidant involvement in the crude isolate, same was the case with the chloroform sub-fraction [68]. The flavonoids were extracted from resinous exudate of H. sinuatum observed significant antioxidant activity (Modak et al., 2005). The methanolic and chloroform extract of entire plant of H. zeylanicum hold significant antioxidant activity along with its antihyperlipidemic and antidiabetic effects (Murugeshet al., 2006). Antiviral and antineoplastic activity The dichloromethane and n-hexane fractions of ethanol extract of the aerial parts of H. subulatum and its subsequent crude isolate was studied for substantial antiviral and antineoplastic activities. For antiviral activity, it was shown that the hexane and ethanol crude isolates exhibited significant activity to Poliomyelitis, Coxsackie, and Measles at concentrations of 500 & 100 μg/ml respectively. For antineoplastic activity, it was found that n-hexane, dichloromethane, and ethanolic extract fractions showed substantial activity with the inhibition of 22.5 & 16.1%, 09.6 & 06.4%, and 19.3 & 32.2% at the dose of 50 and 100 μg/kg/day (Singh et al., 2002a, 2002b). Fig. 2. Some of flavonoids isolated from the genus Heliotropium. Anti-inflammatory activity The crude extract of the entire plant of H. strigosum and its subsequent solvent fractions demonstrated anti-inflammatory activity in xylene-induced ear oedema and carrageenan-induced oedema. When the extracts were tested against xylene-induced ear oedema, hexane and ethyl acetate fractions were found active with 35.77% and 38.21% inhibition, respectively. In carrageenan-induced oedema, the ethyl acetate fraction was most prevailing with 73.33% inhibition followed by hexane fraction (70.66%) (Khan et al., 2013). The extract of chloroform from dried leaves of H. indicum exhibits significant anti-inflammatory activity in cotton pellet granuloma and carrageenan-induced oedema in the models of inflammation. The extract of H. indicum, compared to the positive control drug, diclofenac sodium with a concentration of 150 mg/kg body weight showed a maximum inhibition of 80.0 percent on carrageenan-induced raw paw oedema (Kalyan et al., 2007). 20 mg/ml of the isolate respectively (Osungunna and Adedeji, 2011). The essential oil of H. europaeum acquired from the hydro-distillation process were examined on E. coli, S. typhi, B. subtilis, and S. aureus. The results exhibited the major antibacterial activity against S. typhi and B. subtilis respectively (Saeedi and Morteza-Semnani, 2009). Different methanolic extract fractions such as petroleum ether, chloroform, aqueous fraction, and ethyl acetate of aerial parts of H. bacciferum exhibited remarkable antibacterial activity against E. coli, S. aureus, P. aeruginosa, B. cereus, and S. enteritidis. The fraction of petroleum ether and chloroform demonstrated that it inhibits the growth of B. cereus, P. aeruginosa, and S. aureus with MIC of 15.625 𝜇g/ml, E. coli with 125 𝜇g/ml, and S. enteritidis with 62.5 𝜇g/ml respectively. The aqueous extract showed that it averts the growth of S. enteritidis, S. aureus, and B. cereus with MIC of 7.8125 𝜇g/ml whereas, P. aeruginosa and E. coli with 15.625 𝜇g/ml respectively (Rahimifard et al., 2014). Cytotoxicity and phytotoxicity The crude extract of H. strigosum and its resultant fractions possessed strong phytotoxic and cytotoxic activity. In brine shrimp toxicology assays, the fractions of chloroform and ethyl acetate showed strong cytotoxic actions with LD50 8.8 𝜇g/ml and LD50 8.3 𝜇g/ml respectively, followed by relatively weak crude methanolic extract with LD50 909 𝜇g/ml and n-hexane fraction with LD50 1000 𝜇g/ml whereas in the case of phytotoxic activity against L. acquinoctialis, strong phytotoxic effect was exhibited by ethyl acetate fraction with LD50 91.0 𝜇g/ml respectively while plant crude extract chloroform fraction, and n-hexane fraction caused 30.76 ± 1.1%, 50%, and 30.7 ± 1.1% inhibitory action respectively at maximum concentration that is 1000 𝜇g/ml (Shah et al., 2015). From the ethanolic extract of aerial parts of H. subulatum, dichloromethane fractions of extract n-hexane, and crude extract were scrutinized for cytotoxic activity. It was showed that n-hexane fraction showed potent cytotoxic activity at a concentration of 3 mg/ml Antifungal activity Different fractions of methanolic extract of entire plant of H. strigosum shown prominent antifungal activity. The fractions of n-hexane and chloroform demonstrated antifungal activity against A. fumigatus, A. niger, A. flavus, and F. solani with the MIC of 2.5 mg/ml. Crude isolate was inactive against A. flavus but exhibited activity against A. fumigatus, F. solani, and A. niger with MIC of 2.5 and 3.5 mg/ml. Ethyl acetate and aqueous fractions did not show activity against any fungal strain [68]. The chloroform, ethanolic, petroleum ether, residue, and aqueous extracts of leaves and stem of H. curassavicum showed significant in vitro antifungal activity. The diffusable metabolites of H. curassavicum revealed remarkable inhibitory effects against P. citrinum followed by C. albicans (Mandeel and Taha, 2005). The alcoholic extract of the 6 M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 of accidental ingestion of these Heliotropium species. The toxicity of pyrrolizidine alkaloids appears in the form of liver injury and they were accountable for hepatic-veno occlusive diseases. A disease which became prevalent in Afghanistan due to intake of wheat crop was spread due to infection with seeds of Heliotropium species (Tandon et al., 1978). The clinical signs associated with liver injury resemble to those associated with hepatic cancers, cirrhosis, Budd-Chiari Syndrome with portal hypertension and destruction of narrow hepatic veins due to crosslinkage of DNA strands, damage to hepatocytes due to the production of pyrrole metabolites by microsomal oxidation of pyrrolizidine alkaloids. Pyrrolizidine alkaloids induce dose-dependent necrosis or mitosis inhibition but independent on route of administration (McDermott and Ridker, 1990; Ridker et al., 1985). A disease in broiler chickens has been reported in Australia due to heliotrine, a pyrrolizidine alkaloid extracted from H. indicum. Liver degeneration, depression, and ascites were the clinical symptoms associated with this disorder. The consumption of H. europaeum was demonstrated in Laboratory of Australia, developed similar lesions in this species that were seen in the natural disease due to the presence of heliotrine and lasiocarpine (Pass et al., 1979). On the other hand, the plant showed different and valuable pharmacological actions. (Singh et al., 2002a, 2002b). The aqueous extract of senescent leaves of H. foertherianum and one of its isolated compounds rosmarinic acid were assessed for its effects against a pacific ciguatoxin (P-CTX-1B) in the neuroblastoma cytotoxicity assay and the receptor-binding assay. The cytotoxicity elicited by P-CTX-1B was inhibited by the aqueous extract of H. foertherianum at concentrations up to 2734 μg/ml and by rosmarinic acid up to 607 μg/ml, the concentrations at which they activated to be cytotoxic (Rossi et al., 2012). The methanolic extract of dried plant material of the aerial parts of H. zeylanicum was studied for cytotoxicity in vitro against MRC5 human cell line. The extract revealed significant cytotoxic activity with an IC50 of 13.00 μg/ml (Abdel-Sattar et al., 2009). The methanolic extract of the dried roots of H. indicum was studied for considerable cytotoxic activity by using the brine shrimp lethality bioassay. The extract showed different mortality rate at different concentrations with the LC50 of 47.86 𝜇g/ml and LC90 of 75.85 𝜇g/ml respectively (Rahman et al., 2011). Analgesic activity The ethanolic and aqueous extract from fresh plant of H. indicum exhibited substantial analgesic efficacy in the formalin-induced pain model in mice. For contrast the effect of analgesic, diclofenac sodium and morphine were used as a reference NSAID and opioid respectively. At the dosage of 30–300 mg/kg, both the first and second phases of formalin-induced nociception were inhibited by ethanol and aqueous extracts in a dose-dependent manner. In acute toxicity tests, oral administration of aqueous extract at a dosage of 1–5 g/kg in formalin-induced mice was tolerated, but oral administration of 1–2 g/kg of extracts in sprague-dawely rats induced pathological effects on the kidneys, heart, lungs, and liver. Therefore, instead of providing analgesic action for aqueous and ethanolic extracts, it may have combined toxic effects. Continuing and prolonged use is also not recommended (Boye et al., 2012). Conclusion Heliotropium species has the tremendous potential for phytochemical, botanical, pharmacological and nutritive properties. It is found from the above systemic review and description that Heliotropium has traditionally been used as a curing agent in different countries for the management of multiple inflammations, rheumatism, gout, poisonous bites, and skin diseases. Due to the isolation of bioactive secondary metabolites viz. pyrrolizidine alkaloids, flavonoids, quinones, and terpenoids, Heliotropium species are highly appreciated for antimicrobial and antioxidant activities in this review. In addition, antiviral, anti-inflammatory, anti-diabetic, anti-tumor, gastroprotective, and anti-hyperlipidemic activities, will also improve the therapeutic importance of Heliotropium in future. The pyrrolizidine alkaloids which abundantly present in Heliotropium are liable for their toxic existence such as hepatotoxicity, hepato-carcinogenicity, and mutagenicity. The poisonous nature of pyrrolizidine alkaloids is due to several reasons, such as the plants eaten in food and often utilized in the form of herbal remedies, which are the primary source of these alkaloids. To overcome pyrrolizidine alkaloid poisoning, the ingestion of additional plant materials must be evaded. Although this clear evidence that plants of the Heliotropium genus have several medicinal importance in the treatment of diverse diseases. The medicinal use of these plants as phyto-pharmaceuticals would depend on the production of the required systematic procedures necessary to standardize the various bioactive secondary metabolites in such herbal formulations. Therefore, we conclude that in the coming period, plants of the Heliotropium genus would become an acceptable source of indigenous medicines. Antifertility activity The benzene and n-hexane fractions of the ethanolic extract of H. indicum were examined for antifertility activity in rats using abortifacient and anti-implantation models. The study showed that at the dosage of 200 & 400 mg/kg body weight, the effect of ethanolic extract and its benzene and n-hexane fractions on percentage pre-implantation lost in pregnant rats were 30% and 35%, 30% and 50%, 40% and 60%, while the effect of ethanolic extract and its fractions on percentage abortion in pregnant rats were 30% and 60 %, 50 % and 60%, 50% and 60% respectively. Therefore, the study revealed that H. indicum has better abortifacient activity and moderate sperm motility and anti-implantation (Savadi et al., 2009). Wound healing activity The methanol, chloroform, petroleum ether, and aqueous isolates of H. indicum leaves were individually tested for their activity of wound healing in rats using incision, excision (infected and normal), and dead space wound models. The group of animals treated with methanol extract showed significant healing efficacy with an epithelialization duration of 16.23 ± 0.98 days in the incision wound infection model, relative to the group of animals treated with the regular medication of nitrofurazone with an epithelialization period of 13.5 ± 1.54 days. In this model, it is also found that the treated animals with aqueous and methanol extract exhibited a substantial improvement in wound breaking strength up to 378.63 ± 18.02 g and 478.55±12.63 g, although the other extracts failed to yield significant results (Dash and Murthy, 2011). A brief description of their activities presented in a tabular form (Table 3). Author statement I respectfully submit the attached manuscript titled “Heliotropium; a genus rich in pyrrolizidine alkaloids: A systematic review following its Phytochemistry and Pharmacology” for publication in Phytomedicine. Marwa A.A. Fayed: Conceptualization; Data curation; Formal analysis; Funding acquisition; Investigation; Methodology; Project administration; Resources; Software; Supervision; Validation; Visualization; Roles/Writing – original draft; Writing – review & editing. Discussion Despite the tremendous advantages, species of Heliotropium genus are very noxious in environment due to availability of pyrrolizidine alkaloids. Human deaths in several countries are recorded because Declaration of Competing Interest The author declares that there is no conflict of interest to report. 7 M.A.A. Fayed Phytomedicine Plus 1 (2021) 100036 Funding Hussain, S., Jamil, M., Ullah, F., Khan, A., Ullah, F., Arfan, M., 2010. Antimicrobial and antioxidant activities of the plant Heliotropium strigosum. Afr. J. Biotechnol. 9 (45), 7738–7743. Jain, S., Singh, B., Jain, R., 2001. Antimicrobial activity of triterpenoids from Heliotropium ellipticum. Fitoterapia 72 (6), 666–668. 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