Antibacterial compounds in different species of Datura : A review

The growing phenomenon of antibiotic resistance to pathogenic microorganisms has led to the concern of scientists on finding novel antimicrobial agents from natural sources. Datura species is a medicinal plant that has significant antibacterial properties and has been widely used to treat various diseases such as diabetes, leucoderma, skin disorders, ulcers, bronchitis, jaundice, hysteria, insanity, heart disease, fever, piles, etc. In this review, we focused on the antibacterial characteristics of plant with special reference to phytocompounds studied by various scientists in different species of Datura. Studies showed that maximum antibacterial work has been done on Datura metal, Datura inoxia and Datura stramonium against Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa. Leaves were found to be most promising part as a source for antibacterial activities. Steroidal (51, 71 dimethyl 61– hydroxyl 31, phenyl 3 α-amine β–yne sitosterol) and β-carboline(1,7 dihydroxy-1-methyl 6,8dimethoxy β-carboline) alkaloids are the two antibacterial compounds isolated from D. metel. Research showed that the Datura species are very promising plants for isolation of new antibacterial compounds.


INTRODUCTION
Medicinal plants used as sources for therapeutic agents represent a rapidly expanding area of health science (Chopra et al., 1956).It is now believed that traditional use of the medicinal plants has fewer side effects over allopathic medicine.Such promising facts led to development of herbal derived medicines all over the world (Pal and Shukla, 2003).Datura as a medicinal plant, is a genus of nine species (Datura ferox, Datura inoxia, Datura metel, Datura stramonium, Datura ceratocaula, Datura discolor, Datura leichhardtii, Datura quercifolia and Datura wrightii) of vespertine flowering plants belonging to the family Solanaceae (Nightshade family).The name Datura comes from the early Sanskrit Dustura or Dahatura (Mann, 1996).They are commonly called thorn apple, stink weed, devil's apple, jimson weed, angel's trumpet, etc. (Heiser, 1969;Avery et al.,1959).All the species are woody, stalked leafy annuals and short lived perennials which can reach up to two meters in height.The leaves are alternate with lobed or toothed margin.The flowers are erect, trumpet shaped, 5-20 cm long and 4-12 cm broad at the mouth, colors vary from white to yellow, pink and pale purple.The fruit is spiny capsule.They normally have 12 pairs of chromosomes (Howard, 1989;Liogier, 1995;Burkill, 2000;Bonde, 2001;Stevens et al., 2001).It is very difficult to differentiate between species of Datura, because some species, such as D. wrightii and D. inoxia, are almost similar in appearance.They can change their size and shape of leaf, flower and fruit depending on location.When growing in a moist location, they grow half as tall as a person, but when growing in a very dry location, they only grow into a thin and short plant (Preissel and Preissel, 2002).
All Datura plants were commonly known to contain tropane alkaloids such as scopolamine, hyoscyamine and atropine (Oliver, 1986).Because of the presence of these substances, it has been used for a long time in some cultures as a poison and hallucinogen (Adams and Garcia, 2005).It is also widely used in phytomedicine to cure diseases and was regarded as antispasmodic, intoxicant, germicidal, anodyne antipyretic, antiseptic, antiphlogistic, antiproliferative, antidiarrhoeal, antihelminthic, alexiteric and useful in leucoderma, skin disorders, insanity, catarrh, ulcers, bronchitis, heart disease, jaundice and for fever and piles (Agharkar, 1991;Duke and Ayensu, 1985;Ali and Shuab, 1996;Dabur et al., 2004;Chopra et al., 1968Chopra et al., , 1986)).
In the present review, we studied antibacterial compounds from different species of Datura

Antibacterial compounds in Datura Inoxia
D. inoxia is also known as thorn-apple, moonflower, sacred Datura.The species was first described by English botanist Philip Miller in 1768.Many studies were done on their antibacterial activity and phytocompounds.Gachande and Khillare (2013), showed antimicrobial activity of ethanolic leaf extract of D. inoxia against Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Proteus vulgaris and Salmonella typhi.Jamdhade et al. (2010) studied the antibacterial activity of aqueous extracts of different parts of D. inoxia (root, stem, leaf, seed and fruit coat) against five human pathogenic bacteria viz.Bacillus megaterium, Bacillus cereus, E. coli, S. typhi and S. aureus.The results indicated that aqueous extract of leaf showed potential antibacterial activity against the tested pathogens.Kaushik and Goyal (2008), also investigated antibacterial activity of D. inoxia (leaf, stem and root) ethanol, methanol, hexane and ethyl acetate extracts against Gram-negative bacteria (E. coli and S. typhi) and Gram-positive bacteria (B.cereus, B. subtilis and S. aureus).Extracts prepared from leaves were shown to have better efficacy than stem and root extracts.Among all the extracts, methanolic extract was found to be most active against all the bacterial species tested.Alwan et al. (2011), studied in vitro antibacterial activity of D. innoxia dried leaves against E. coli and S. aureus.The antibacterial activity of D. innoxia ethanolic extract showed that E. coli was more sensitive than S. aureus, Phytochemical analysis revealed the presence of alkaloids, flavonoids and tannins in the extract.

Antibacterial compounds in Datura metel
This species is also known as devil's trumpet, it was first described by Linnaeus in 1753 and studied by many scientists for its antibacterial properties and phytocompounds.Okwu and Igara (2009), isolated and identified a new antibacterial steroidal alkaloid (5¹, 7¹ dimethyl 6¹-hydroxyl 3¹, phenyl 3 α-amine β-yne sitosterol (Figure 1 and Table 1) from D. metel leaves ethanolic extract using ¹³C, ¹H NMR, IR and MS spectroscopic data.Compound showed antibacterial activity against S. aureus, P. aeruginosa, Proteus mirabis, S. typhi, B. subtilis and K. pneumonia but could not inhibit E. coli.Vadlapudi and Kaladhar (2012), evaluated antimicrobial activity of aerial parts of D. metel L. against the resistant pathogens such as L. acidophilus, P. marginalis, Pseudomonas syringae, P. aeruginosa, S. mutans, Streptococcus salivarius and S. aureus.The plant parts were extracted using methanol, hexane and chloroform solvents.Results of agar well diffusion method revealed that methanol and chloroform extracts exhibited promising antimicrobial activity than hexane extracts.
Ethanolic extract from leaf of D. metel showed potential antimicrobial activity against B. subtilis, E. coli, S. aureus, P. vulgaris and S. typhi (Gachande and Khillare, 2013).Sakthi et al. (2011), studied antibacterial potentiality of ethanol and ethyl acetate extracts of mature leaves of D. metel against S. aureus, B. subtilis, B. cereus, E. coli, S. typhi, Shigella flexneri, Klebsiella pneumoniae, Vibrio cholera and P. aeruginosa.The ethanol extract of D. metel showed maximum zone of inhibition against P. aeruginosa, E. coli and B. subtilis.S. aureus showed less zone of inhibition.The ethyl acetate extract of D. metel showed maximum zone of inhibition against E. coli.There was no zone of inhibition against P. aeruginosa.Phytochemical analysis revealed the presence of compounds like alkaloids, tripenoid, steroids, flavonoid, extracts.Phytochemical analysis revealed the presence of saponin, flavonoids, tannins, phenols and alkakoids, glycocides, steroids and terpenoids of which steroids, terpenoids and tannins were absent in the ethanol extract.

Datura stramonium
D. stramonium is commonly known as jimsonweed, thorn-apple and moon flower.It was scientifically described and named by Swedish botanist Carl Linnaeus in 1753 and was studied by many scientists for their antibacterial properties and phytocompounds.Ethanolic leaf extract from D. stramonium showed potential antimicrobial activity against B. subtilis, E. coli, S. aureus, P. vulgaris and S. typhi (Gachande and Khillare, 2013).The antimicrobial activity of D. stramonium (leaf ethanolic extract) studied by Banso and Adeyemo (2006), were assessed against P. aeruginosa, K. pneumonia and E. coli.The plant showed significant antibacterial activity against the tested pathogens.Phytochemical analysis revealed the presence of saponins, tannins, alkaloids and glycosides.Kumar et al. (2010), investigated the antibacterial activity of D. stramonium (leaf ethanolic extract) against three standard microorganisms, E. coli, Bacillus amyloliquefaciens and P. aeruginosa.The plant has been found to show antibacterial activity against P. aeruginosa but not against E. coli and B. amyloliquefaciens.
The in vivo and in vitro antimicrobial activity of different parts of D. stramonium (leaf, fruit, stem, root and callus) were investigated by Sharma et al. (2013), against E. coli, S. aureus and P. aeruginosa.All the solvent extracts (ethanol, methanol, petroleum ether and aqueous) showed significant antimicrobial activity against all the tested micro-organisms.Methanolic extract was most active against all micro-organisms, whereas all the extracts showed significant activity against P. aeruginosa.Jamdhade et al. (2010), studied antibacterial activity of aqueous extracts of different parts of D. stramonium (root, stem, leaf, seed and fruit coat) against five human pathogenic bacteria viz.B. megaterium, B. cereus, E. coli, S. typhi and S. aureus.The results indicated that aqueous extract of leaf were most effective against all the tested pathogens.The phytochemical analysis and antimicrobial activities of in vitro grown callus and D. stramonium methanolic extracts of root, stem, leaves, fruits, callus and crude metabolite rich fractions were studied by Sharma and Sharma (2013), against E. coli, S. aureus and P. aeruginosa.The crude extracts from D. stramonium were analyzed for moisture, starch, carbohydrate, ascorbic acid, lipid, proline, crudeprotein, phenols, DNA, RNA, chlorophyll and carotenoid in plant parts and callus.The results indicated that methanolic leaf extract exhibited better antimicrobial activity against S. aureus, E. coli, P. aeruginosa.In the metabolite rich fraction (flavonoids, phytosterols and alkaloids), greatest bactericidal activity was exhibited by flavonoids against P. aeruginosa.Gul et al. (2012), studied antibacterial activity of D. stramonium branches and leaves samples in three different solvents benzene, chloroform and ethanol against Enterobacter, Micrococcus luteus, Pseudomonas aeruginosa, E. coli, S. aureus and K. pneumonia.All the solvent extracts showed significant antibacterial activity against tested pathogens.Comparative minimum inhibitory concentration of benzene, chloroform and ethanol extract determined that benzene extract was very effective against all bacterial strains.The antimicrobial activity of ethanolic leaf extract of D. stramonium L. (Solanaceae) were evaluated by Reddy et al. (2009), against K. pneumoniae, S. typhi, S. aureus, P. vulgaris, P. aeruginosa and E. coli.The alcoholic extract of the plant has shown promising antimicrobial activity and effectively inhibited the growth rate of S. aureus, S. typhi, P. aeruginosa and E. coli but K. pneumonia and P. vulgaris were found resistance.Phytochemical studies revealed the presence of alkaloids, glycosides, reducing sugars, tannins, steroids, terpenoids, phenols, flavonoids, proteins, saponins and amino acids in the extract.
Joshi and Kaur (2013)nolic extracts of the plant parts have shown mild to strong antimicrobial activity.Joshi and Kaur (2013), worked on antimicrobial activity of ethanol, methanol and aqueous extract of D. innoxia leaf against four pathogenic bacteria: E. coli, Staphylococcus epidermidis, P. aeruginosa, and B. subtilis.Results showed that the extracts of D. innoxia have potent antimicrobial activity against pathogens.

Table 1 .
Summary of review showing comparative work of different scientist in different species of Datura.