Abstract

Two triterpenes were isolated from the chloroform extract of Protorhus longifolia. Theirstructures were established through spectral analysis (nuclear magnetic resonance (NMR), infrared (IR), liquid chromatography mass spectrometry (LC-MS)) as 3-oxo-5α-lanosta-8,24-dien-21-oic acid (1) and 3β-hydroxylanosta-9,24-dien-24-oic acid (2). The two triterpenes were screened for their antioxidant, cytotoxicity, anti-platelet aggregation and anti-inflammatory activity. The antioxidant activity of the compounds was measured using 1,1′-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) free radicals scavenging and reduction potential assays. The cytotoxic effects of the compounds was determined against human embryonic kidney (HEK293) and human hepatocellular carcinoma (HepG2) cell lines, while the acute anti-inflammatory activity was determined using the carrageenan-induced rat paw edema model. The anti-platelet aggregation activity of the compounds was separately investigated on thrombin, adenosine diphosphate (ADP), epinephrine and arachidonic acid induced rat platelet aggregation. Although, both compounds exhibited poor antioxidant activities, they showed good concentration dependent anti-platelet aggregation activity. The highest activity by compound 1 (IC₅₀ of 0.99 mg/ml) was observed on the thrombin-induced platelet aggregation. Compound 2 (3 mg/ml) exhibited anticoagulant activity on whole blood and significantly (P < 0.05) inhibited the acute inflammation of rat paw. The compound also weakly inhibited the growth of HEK293 and HepG2 cells. The triterpenes could be potential pharmacologically active anti-platelet aggregation agents.

Key words: Triterpenes, antioxidant, anti-inflammatory, anti-platelet aggregation, cytotoxicity.