Plant species richness regulated by geographical variation down-regulates triterpenoid compounds production and antioxidant activities in white birch bark

Abstract

White birch (Betula platyphylla Suk.) is a pioneer tree species widely distributed in the high northern hemisphere, and its bioactive compounds have ecological and traditional medicinal roles. How ecological factors impact triterpenoid production is not well understood yet. This study examined the effects of geo-climate, soil properties and plant community properties on triterpenoid compounds synthesis and antioxidant activities of white birch bark at eight locations (13° latitude and 6° longitude ranges) in Northeast China. The results showed that the contents of total triterpenoids, betulin and betulinic acid in white birch bark were high at higher latitudes, and low at lower latitudes. The antioxidant activity of the extracts analyzed by DPPH (1, 1-diphenyl-2-picrylhydrazyl), ABTS (2, 2-azinobis-3-ethylbenzothiazoline-6-sulphonic acid), and FRAP (ferric reducing antioxidant power assay) methods varied across different locations and positively correlated with triterpenoid compound contents. Redundancy analysis indicated that more than 40% of the secondary metabolite variations could be explained by plant species richness in the community, largely regulated by geographical variation. Our findings highlighted that higher species richness reduced triterpenoid accumulation and antioxidant potential. At the same time, the harsh environments in cold and dry geo-climate increased triterpenoid production of white birch. This study favors the efficient use of white birch for triterpenoid production and implies that the stress of harsh environment will promote the synthesis of the secondary metabolite synthesis of dominant trees.