Careya arborea stem bark: source of potential therapeutic agents

Abstract

Natural products originating from plants and microorganisms have been widely used to treat many diseases. Many records have shown the use of such substances by humans for thousands of years. Careya arborea, commonly known as wild guava, is a medium-sized deciduous tree that belongs to the Family Lecythidaceae. The stem bark is used in the treatment of tumours, bronchitis, epileptic fits and skin diseases. It is also used as a remedy for diarrhoea dysentery with bloody stools and ear pain. Careya arborea stem bark was air-dried and powdered using a grinder. The powdered sample was sequentially extracted with ethyl acetate (EtOAc) and methanol (MeOH) using a sonicator. Removal of the solvents afforded EtOAc and MeOH extracts. The two extracts were subjected to silica gel, Sephadex LH-20 and reversed-phase silica gel columns to yield five compounds Lupeol caffeate (1), Epigallocatechin-3-gallate (2), Gallocatechin (3), Epigallocatechin (4) and Lupeol (5). All the compounds were subjected to enzyme inhibitory assays; α-amylase, α-glucosidase, acetylcholinesterase and lipase. Compounds were screened for antioxidant activity using DPPH radical scavenging method, antifungal activity against Cladosporium cladosporioides, phytotoxicity by lettuce seed germination assay and toxicity against brine shrimp, Artemia salina. Compound 2 showed moderate brine shrimp lethality (LD₅₀ 71.29 ppm). Strong antioxidant activity against DPPH radical was observed for all five compounds, and strong α-glucosidase inhibitory activity was observed for compounds 2, 3 and 4 (IC₅₀ 0.89, 3.80 and 0.25 ppm, respectively). Moderate acetylcholinesterase inhibitory activity was exhibited by compound 2 (IC₅₀ 85.92 ppm) and compound 5 (IC₅₀ 90.33 ppm), while compound 3 showed strong acetylcholinesterase inhibitory activity (IC₅₀ 9.51 ppm). Out of all, compound 3 exhibited mild α-amylase inhibitory activity (IC₅₀ 111.81 ppm), and compound 2 showed lipase inhibitory activity (IC₅₀ 179.85 ppm). These results suggest that C. arborea could be a potential source for the isolation of new therapeutic agents.