Chemical composition and biological propensities of Wikstroemia indica (L.) C. A. Mey (Tie Bush)

Abstract

Wikstroemia indica (L.) C. A. Mey. (Thymelaceae) is well documented for use in traditional medicine, but scientific studies on this plant species are lacking. Hence, its phytochemical and pharmacological properties were investigated using different methods. The total phenolic (66.00 ± 0.44 mg GAE/g), flavonoid (69.96 ± 0.32 mg RE/g), phenolic acid (32.59 ± 1.29 mg CE/g) and flavonol (4.46 ± 0.07 mg CAE/g) content of the methanolic extract (ME) was highest when compared to the ethyl acetate extract (EAE) and aqueous extract (AE) respectively. Altogether, 31 compounds were identified by HPLC (High Performance Liquid Chromatography) method. The DPPH (2,2-diphenylpicrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), FRAP (Ferric reducing antioxidant power assay), assays demonstrated that the ME had the highest antioxidant potential with recorded values of 188.38 ± 0.22, 421.31 ± 14.54, 397.10 ± 2.68 and 651.19 ± 16.90 mg TE/g respectively. Regarding the acetylcholinesterase, the ME and the EAE were the best inhibitors (3.13 ± 0.11 and 3.11 ± 0.14 mg GALAE/g). Only the EAE was active against the butyrylcholinesterase enzyme with recorded value of 7.05 ± 0.14 mg GALAE/g. The tyrosinase inhibitory assays demonstrated that the extract inhibitory potential was in the following order: ME (117.63 ± 2.53 mg KAE/g) > EAE (112.57 ± 0.85 mg KAE/g) > AE (13.65 ± 0.87 mg KAE/g). The alpha amylase inhibitory potential of the EA and ME were the same (0.68 ± 0.01 mmol ACAE/g) and better than the AE (0.10 ± 0.01 mmol ACAE/g). HT 29 treated with W. indica in aqueous started to exhibit cell cytotoxicity from 500 µg/mL. The IC50 value exhibited at 786.14 µg/mL. W. indica can be developed into extracts to promote general health pending toxicological studies that show the plant is entirely safe for human consumption.