Effects of dipterocarpus alatus leaf and bark extracts on uvb-protection, collagen stimulating activity and nitric oxide inhibition

Abstract

Dipterocarpus alatus (D. alatus) is used for the treatment of rheumatism in Ayurvedic medicine. In this research, the leaf and bark ethanol extracts of D. alatus were investigated for antioxidant activity, UV-protection on HaCaT keratinocytes, inhibition of nitric oxide formation on RAW 264.7 macrophages and collagen proliferation on normal human dermal fibroblasts (NHDFs). The total phenolic and total flavonoid contents of the leaf and bark ethanol extracts were determined using Folin-Ciocalteu assay and AlCl3 assay, respectively. Cell viability of HaCaT keratinocytes, RAW 264.7 macrophages and normal human dermal fibroblasts (NHDFs) were evaluated including cell morphology, collagen production, nitric oxide inhibition. The leaf extract showed the highest phenolic content (1,327.07 ± 95.37 gGAE/100 g dry weight), flavonoid content (343.23 ± 21.36 gQE/100 g dry weight), and ferric reducing power (4.05 ± 0.34 mM FeSO4/100 g dried weight), whereas the bark extract showed better DPPH and ABTS assays (IC50 at 13.88 ± 0.27 and 28.15 ± 0.54 µg/mL, respectively). Both leaf and bark extracts showed no toxicity on HaCaT cells and NHDFs at 1-500 µg/mL, but the leaf extract above 25 µg/mL and bark extract above 100 µg/mL showed toxicity to Raw 264.7 cells. The leaf extract at 50 µg/mL presented more UVB protective effect than the bark extract with no toxicity to UVB-induced HaCaT cells. The bark extract induced higher collagen production and nitric oxide inhibition than the leaf extract. The leaf extract of D. alatus showed beneficial potential for inclusion in UV protection products, whereas the bark extract is suited for wound healing products.