An evaluation of the antioxidant capacities of Dillenia excelsa extracts and its wound healing activity in Wistar rats

Abstract

Dillenia excelsa, a medicinal plant found in Brunei Darussalam, has been traditionally used by locals for treating various ailments. The present study aims to investigate the presence of phytochemicals, antioxidant properties, antibacterial activities and wound healing potential of methanolic extracts of the leaves, fruits, flowers and bark of Dillenia excelsa. Phytochemical screening using frothing test, Salkowski test, Dragendorff’s test and ferric chloride test revealed the presence of saponins, steroids, terpenoids, alkaloids and tannins. The total phenolic content (TPC) investigated using Folin-Ciocalteu reagent and total flavonoid contents (TFC) assessed using aluminium chloride colorimetric assay yielded the highest value of 106.3 ± 2.6 mg gallic acid equivalent per gram (GAE/g) of crude leaves extract and 23.1 ± 0.5 mg quercetin equivalent per gram (QE/g) of crude leaves extract, respectively. The antioxidant capacities of the extracts were assessed and showed the leaves extract has the highest 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity and ferric ion reducing antioxidant power with the value of 156.2 ± 59.3 mg GAE/g of crude extract and 2.77 ± 0.33 mg Trolox equivalent per gram (TE/g) of crude extract, respectively. Antibacterial activities against two gram-positive and two gram-negative strains using agar well diffusion method revealed only the flowers extract showed inhibition against Bacillus subtilis with minimum inhibitory concentration of 40 mg/mL. The in vivo wound healing potential was also carried out using male Wistar rats. The high dose leaves extract (50% w/w) showed the highest reduction in wound size at day 7, 10 and day 14 compared to the control groups and other treatment groups. Based on this present study, D. excelsa was shown to have the potential to promote wound healing and may serve as part of the armamentarium to traditional and complementary medicine.