Alstonia venenata R. Br, a member of family Apocynaceae is known for its medicinal value and considered as a powerful antidote for poisonous snake bites. The antibacterial effect of the crude leaf and stem bark extracts in solvent systems like hexane, benzene, isopropanol, ethyl acetate, methanol, and water were investigated. The isopropanol and methanol crude leaf extracts and benzene stem bark extract showed significant antibacterial activity against pathogens and Bacillus sps. The crude leaf extracts, which showed biological activity were fractionated and active compounds identified by thin layer, and column chromatography and other qualitative methods. They consisted of alkaloids, sterols, sterol glycosides and other polyphenols. All were analyzed for antibacterial properties.
venenata R. Br (Family: Apocynaceae) is a medium-sized
evergreen shrub found in the southern parts of India, sparsely
distributed on the Ponmudi and Annamalai Hills, requiring
wet soil and shade. The plant is particularly important
by virtue of its medicinally important plant parts which
include root bark, a powerful antidote against venomous
snake bites. The bark, roots, latex, and leaves are used
by folklore in traditional medicine. In tropical countries
(Africa and Asia), the bark and roots are used to treat
malaria, toothache, rheumatism, diarrhoea, snakebite, sores,
etc. Latex is used in drinks to treat coughs, sore throat,
fever, eye ailments including corneal infections. The ripe
fruits are used for syphilis, insanity and epilepsy in Indian
medicine. The compounds reported in Alstonia venenata
include the root bark alkaloids Venenatine (antifungal) (Singh et al., 2000), 5-methoxy-1-oxo-tetrahydro-b-carboline (Banerji et al., 1981), stereomeric 16-epivenenatine
and 16-epialstovenine (Chatterjee et al.,
1981), echitoserpidine (fruit alkaloid) (Majumder
and Dinda, 1974), venoterpene (monoterpenoid fruit alkaloid) (Ray and chatterjee, 1968). Most of the active compounds
include alkaloids and sterol glycosides. The plant is an
active ingredient of Tri Health Ayurvedic formulations,
such as Mahathiktakam Kwath and Gritham.
specimens of Alstonia venenata were collected from
their natural habitats in the Kallar region, Ponmudi Hills,
South India. The leaves were removed, shade dried and powdered.
Quantitative analysis, in terms of fresh weight, dry weight,
powder weight and moisture loss, was noted. 20 g of the
powdered material was extracted successively with hexane,
benzene, 2-propanol, ethyl acetate, methanol and finally
water, and each extract was concentrated by distilling off
the solvent and then evaporate to dryness on the water bath.
While the isopropanol extract showed the maximum weight
(4.40 g), ethyl acetate showed the minimum (0.19g).