Ayurvedic practitioners employ several Terminalia arjuna preparations for the treatment of cardiovascular disorders and for their lipid lowering activities.
A large number of pentacyclic tritepenoids, flavonoids and tannins have been reported from the bark. The principal triterpenoids are arjunolic acid (the main constituent- and its glycosides), arjunic acid (its glycoside arjunetin,arjunoside I –IV), arjungenin, terminoside, terminic acid etc. The flavonoids include arjunolone, baicalein , flavones, kampferol, pelorgonidin , quercetin and luteolin. Hydrolysable tannins include arjunin, pyrocatechols, punicalin , punicalagin , terchebulin , terflavin C , castalagin , casuariin and casuarinin.
Among these ,compounds with cardiovascular effects are beta -sitosterol, terminic acid, terminoside A, arjunolone, baicalein, pelorgonidin, punicallin, terchebulin, terflavin, and castalagin.
Powdered tree bark is considered particularly useful. It is used to alleviate angina, possibly via its antioxidant activity. The stem bark contains high levels of antioxidant compounds, including glycosides, flavonoids, tannins and inorganic minerals.
The Cardioprotective effects noted for T. arjuna bark extracts include increases in coronary flow and decreased blood pressure. Furthermore, enhanced prostaglandin E2 (PGE2) activity, As PGE2 is known to produce coronary vasodilation, this increase may be responsible for the increased coronary flow following T. arjuna treatment. Bark extracts of T. arjuna also reverse cardiac injury and have cardiovascular protective and tonic effects including improved cardiac cell mitochondrial uptake, protection against oxidative stress and decreased levels of lipid peroxidase activity Further cardio-protective effects of T. arjuna bark include decreases in total lipid levels, especially LDL lipids, with a coincident increase in HDL lipids.
Among the antioxidant compounds, flavonoids and tannins are present abundantly in T.arjuna bark. It contains very high levels of flavonoid compounds compared to other plants. Indeed, one study estimated the total flavonoid levels in T. arjuna bark are 3 times that of Cinnamon, and 5 times that of tea leaves, capsicum and turmeric. They prevent oxidation of LDL cholesterol via their free radical scavenging activity, inhibit endothelial activation and inhibit platelet aggregation, They also possess cyclooxygenase inhibitory activity and can thus prevent thrombosis.
High tannin contents of T. Arjuna enhance nitric oxide synthesis and relax vascular tissue stimulated to contract by norepinephrine and thus may be responsible at least in part for the hypotensive activity of T. arjuna bark. Terminalia arjuna is a particularly interesting plant for the treatment of cardiovascular disorders due to its multiple modes of cardioprotection. Early studies have demonstrated that T. arjuna bark extracts increase the rate and force of cardiac contraction, as well as amplitude of contraction and the cardiac output Furthermore, T. arjuna bark extracts also produce substantial ionotropic effects
Antimicrobial activity Compounds with antimicrobial activity are friedelin, gallic acid, ellagic acid, casuarinin, chebulagic acid and punicalagin. All Terminalia species have a history of usage to treat medical conditions related to microbial infections and numerous recent investigations have reported on their antibacterial properties. Leaf and bark extracts of arguably the best studied Terminalia species, T. arjuna, have been reported in numerous studies to have antibacterial activity against a wide panel of microbes, partially justifying its use in the treatment of a wide range of diseases and medical disorders.
Antiinflammatory activity and immunomodulation. beta-Sitosterol present stimulates smooth muscle cells to release prostacyclin (PGI2) (Awad et al. 2004). Conversely, b-sitosterol treatment blocks the release of PGI2 and prostaglandin E2 (PGE2) from macrophages. Thus, b-sitosterol treatment would be expected to affect vasodilation and, therefore, have a therapeutic effect on inflammation. Recent studies have reported that T. arjuna leaf extracts have potent anti-inflammatory activity in vivo (Biswas et al. 2011). This anti-inflammatory effect is likely due to the inhibition of the enzyme cyclooxygenase, resulting in the inhibition of prostaglandin synthesis
Anticancer activity. The tannin casuarinin isolated from bark has been reported to induce apoptosis in human A549 lung cancer cell lines. It was postulated that an enhanced Fas/APO-1 ratio and increases in membrane bound and soluble Fas ligands may be responsible for casuarinin’s apoptotic effect. Furthermore, casuarinin was also found to arrest cell cycle progression in the G0/G1 phase, possibly due to a p53-dependent induction of p21/WAF1
Antidiabetic activity and analgesic effect was approximately the same efficacy as recorded for acetylsalicylic acid. The T. arjuna study also examined the anti-inflammatory activity of the analgesic extract, reporting significant activity in an assay designed to evaluate the enzyme cyclooxygenase which is responsible for prostaglandin synthesis.
References:
Cock, I.E (2015) The medicinal properties and phytochemistry of plants of the genus Terminalia (Combretaceae) Inflammopharmacol. 23(5):203-29.
Augustine Amalraj and Sreeraj Gopi (2017) Medicinal properties of Terminalia arjuna (Roxb.) Wight & Arn.: A review, Journal of traditional and complementary medicine 7 (1), 65-78
Mammen Daniel
