Plumbago zeylanica is one of the oldest drugs known to Ayurvedic physicians. It is a component of several Indian preparations used as caustics or abortifacients.
Found wild in the tropics and subtropics and widely cultivated as an ornamental plant.
A much-branched shrub with long and tuberous roots and a striate stem (Plate 48). The leaves are up to 8 cm long, simple, glabrous, alternate, ovate or oblong, with an entire or wavy margin, an acute apex and a short petiole. The flowers are white in terminal spikes, with a tubular calyx, a slender, glandular, hairy corolla tube, with five lobes and five stamens, a slender style and a stigma with five branches. The fruit is a membranous capsule enclosed within the persistent calyx. The dried roots occur as cylindrical pieces of varying length, less than 1.25 cm in width, reddish-brown in colour with a brittle, fairly thick, shrivelled, smooth or irregularly fissured bark. The roots have a short fracture, an acrid and biting taste and disagreeable odour.
The drug is an abortifacient and vesicant. It is also used in the treatment of rheumatism, dyspepsia, piles and diarrhoea and as a diuretic. It is used as a counterirritant and for skin diseases. The drug is apt to cause abortion and in Malaysia, eating the leaves is said to cause similar action. In Africa, a cold infusion of the root is used for influenza and black water fever. The powdered root is occasionally taken as a snuff to relieve headache.
The bark is used to stop bleeding in ruminants.' It is also used to cure baldness, cracked tail, worms in the eye, diarrhoea and boils.2 In Java the root is used to expel worms from horses.
The chief component is plumbagin, together with 3-chloroplumbagin, 3,3' -biplumbagin, 3' ,6' -biplumbagin (chitranone), isozeylanicone, zeylanicone, elliptinone and droserone.
Lupeol and lupenyl acetate have been isolated from the root.
Aspartic acid, tryptophan, tyrosine, threonine, alanine, histidine, glycine, methionine and hydroxyproline were isolated from the aerial parts.
Anticancer activity: Plumbagin has been reported as having anticancer activity against fibrosarcoma induced by methyl cholanthrene and P388 lymphocytic leukaemia, but not against L1210 lymphoid leukaemia in mice. It is thought to be an inhibitor of mitosis. It has also been evaluated against Dalton's ascitic lymphoma, where an inhibition of tumour growth and a significant enhancement of mean survival time were observed for treated mice compared to the control group. Peritoneal cell counts were also enhanced. Plumbagin?treated groups were able to reverse the changes in various haematological parameters which are a consequence of tumour inoculation. Studies have shown that plumbagin, when administered orally at a dose of 4 mg/kg body weight, caused tumour regression in rats with 3-methyl-4?dimethyl aminoazobenzene (3MeDAB)-induced hepatoma. It reduced levels of glycolytic enzymes such as hexokinase, phosphoglucoisomerase and aldolase levels, which are increased in hepatoma-bearing rats, and increased levels of gluconeogenic enzymes such as glucose?.6-phosphatase and fructose-I ,6-diphosphatase which are decreased in tumour hosts.
Antifertility activity: In rats, treatment during the first week of pregnancy abolished certain uterine proteins resulting in both pre?implantationary loss and abortion of the foetus. Uterine endopeptidases (cathepsin D, remin and chymotrypsin) were studied after the root powder had induced these effects and cathepsin D and renin activities were found to be decreased whilst chymotrypsin activity was increased. The results indicated that cathepsin D and renin may playa role in maintenance of pregnancy and chymotrypsin may be involved in postabortive involution. Plumbagin, at a dose of I and 2 mg/IOO g body weight, prevented implantation and induced abortion in albino rats without any teratogenic effects, and produced a significant inhibitory effect on copper acetate-induced ovulation in rabbits.
Antiinflammatory activity: A phosphate buffered saline extract of the roots of P. zrylanica stabilised red blood cells subjected to both heat- and hypotonic-induced lyses,A biphasic response and a reduction in the enzymatic activities of alkaline and acid phosphatases were observed and adenosine triphosphate activity was stimulated in liver homogenates of formaldehyde-induced arthritic rats.
Antimicrobial activity: A chloroform extract from P. zeylanica showed significant activity against penicillin- and non-penicillin resistant strains of Neisseria gonorrhoeae. It also showed antibacterial activity against Bacillus mycoides, B. pumilus, B. subtilis, Salmonella typhi, Staphylococcus aureus and others. Eye drops containing 50 llg/ml of plumbagin demonstrated significant antibacterial, antiviral and antichlamydial effects in eye diseases with few side effects. Aqueous, hexane and alcoholic extracts of the plant were found to show interesting antibacterial activity. The alcoholic extract was the most active and showed no toxicity when assayed using fresh sheep erythrocytes.
Antibiotic resistance modification: Plumbagin has been studied for its effect on the development of antibiotic resistance using sensitive strains of Escherichia coli and Staphylococcus aureus. When the organisms were inoculated into the antibiotic (streptomycin/rifampicin) medium, some growth was observed due to development of resistance. However, it was completely prevented when plumbagin was added to the medium and this was attributed to prevention of antibiotic resistance.
Antioxidant activity: At a concentration of 1 mM, plumbagin prevented peroxidation in liver and heart homogenates. By a comparison with menadione (which has one hydroxyl group less) it was suggested that plumbagin may prevent NADPH and ascorbate-induced microsomal lipid peroxidation by forming hydroquinones. These may trap free radical species involved in catalysing lipid peroxidation.
Immunomodulatory activity: The effect of plumbagin was studied on peritoneal macro phages of BALB/c mice, evaluated by bactericidal activity, hydrogen peroxide production and superoxide anion release. The bactericidal activity in vivo of plumbagin-treated mouse macrophages was estimated using Staphylococcus aureus and in low doses plumbagin caused a constant increase in bactericidal activity. It was also seen to exert a similar response on oxygen radical release, showing a correlation between oxygen radical release and bactericidal activity. Plumbagin appeared to augment macrophage bactericidal activity at low concentrations by potentiating oxygen radical release, whereas at higher concentrations it had an inhibitory effect.
Hypolipidaemic activity: When administered to hyperlipidaemic rabbits, plumbagin reduced serum cholesterol and LDL cholesterol by 53-86% and 61-91 % respectively. It also lowered the cho/esteroV phospholipid ratio and elevated HDL cholesterol significantly. Furthermore, plumbagin treatment prevented the accumulation of cholesterol and triglycerides in the liver and aorta and caused regression of atheromatous plaques of the thoracic and abdominal aorta. The animals treated with plumbagin excreted more faecal cholesterol and phospholipids.
Uterine stimulant activity: The juice extracted from the root was found to have potent activity when tested on rat uterus in vitro, as well as on isolated human myometrial strips. This ecbolic effect was not blocked by either atropine sulphate or pentolinium bitartrate.
Anticoagulant activity: Plumbagin significantly increased prothrombin time, GPT, total protein and alkaline phosphatase levels in liver tissue and decreased GPT levels in serum. The anti-vitamin K activity was thought to be associated with the hydroxyl group attached to the naphthoquinone ring ofthe compound.
Digestive effects: The roots of Plumbago zeylanica were found to stimulate the proliferation of coliform bacteria in mice and act as an intestinal flora normaliser. This supports claims that the plant is a digestive stimulant.
The LDso of plumbagin is approximately 10 mg/kg body weight (oral and IP) in mice and a 50% alcoholic extract of the root or whole plant has an LD50 of 500 mg/kg body weight when given IP.26 In view of the documented abortifacient activity, it should be avoided at all stages of pregnancy.