Anti-glycation and Antioxidant Activities of Australian Centella species
The products of nonenzymatic glycation and oxidation of extracellular matrix contribute to the delayed healing of diabetic ulcers. Centella plant species have been used medicinally for various dermatological disorders including wound healing. The aim of this study was to evaluate the anti-glycation and antioxidant activities of the methanolic extract of two species of Australian Centella; Centella asiatica (L.) Urb. (Apiaceae/Umbelliferae) and Centella erecta (L.f.) Fern. The anti-glycation activity of the extracts was assessed by measuring the fluorescence intensity of advanced glycation end products (AGEs) formed after incubating collagen-type I and bovine serum albumin with methylglyoxal (MGO) for two and five days, respectively. The antioxidant activity was evaluated by interrogating the ability of each extract to scavenge DPPH free radicals. The phytochemical profile of both species was also examined by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) analysis. The methanolic extracts (100 µg/mL – 1200 µg/mL) of both species decreased significantly the formation of AGEs induced by MGO in a dose dependent manner. Free radical scavenging inhibition was 80.2 ± 4.4% for C. asiatica and 77.8 ± 3.9% for C. erecta. HPLC and TLC showed the presence of the major Centella saponins (asiaticoside, madecassoside) and their aglycones (asiatic and madecassic acids), phenolic acids (chlorogenic acid) and flavanoids (quercetin, isoquercetin and kaempferol) in both extracts. The results suggest that Centella species are not only capable of inhibiting the glycation of collagen but also exhibit substantial antioxidant activity, which may be clinically effective in impaired wound healing in diabetes.