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The bark of several coniferous species, a waste product of the timber industry, contains significant amounts of natural antioxidants. In our ongoing studies of Nepalese medicinal plants, we examined the bark from Abies spectabilis as the starting material for extracting antioxidant compounds. In vitro antioxidant activity evaluated by means of three antioxidant methods, namely 2,2-diphenyl-1-picrylhydrazyl (DPPH), Briggs-Rauscher oscillating reaction (BR) and Trolox Equivalent Antioxidant Capacity (TEAC) and total phenol contents with the Folin-Ciocalteau reagent; the ferrous iron chelating capacity was also assessed. The methanol extract of A. spectabilis showed significant antioxidant activity and polyphenol contents (IC50 4.13 μg/mL, 0.20 μg/mL eq. resorcinol, 4.22 mM eq. Trolox, 3.9 μg/g eq. gallic Acid in the DPPH, BR, TEAC and Folin-Ciocalteau tests, respectively) and weak Fe2+ chelating capacity. Phytochemical studies were also carried out with 1D- and 2D NMR experiments and DI-ESI-MS, HPLC-DAD and LC-MSn measurements. Oligomeric C-type proanthocyanidins, mainly trimeric gallocatechin derivatives, were the most abundant compounds (16% of extract expressed as procyanindin B1). Gallocatechin oligomers (up to six units) and prodelphynidin-gallocatechin polymers were also identified in the extract. Prodelphynidin B4, cyclograndisolide and trans-docosanil ferulate were also isolated and characterized by NMR and MS spectroscopy. [ABSTRACT FROM AUTHOR]

Abstract: Centella asiatica (L.) Urban is widely used in traditional medicine in many countries and in the formulation of drugs and cosmetics, and is therefore suitable as a trade item for the development of medicinal plants for the population of Nepal. The aim of this work was to select plant populations of C. asiatica with high contents of secondary metabolites growing in various localities in Nepal, and to enhance knowledge of the cultivation of this plant. Quali-quantitative analysis of bioactive triterpenes (asiaticoside and asiatic acid) and phenol derivatives (flavonoids and caffeoyl esters) was performed by HPLC-DAD-ELSD. The highest quantities of triterpenes and phenols were found in samples from the Gorkha and Chitwan districts. Regarding cultivated plants, soil fertilisation is critical, since over-rich soils affect secondary metabolite content. Plants growing in sand-rich soils produce more terpenes. This work provides indications on how to select high-terpene producing germplasm and recommendations for plant cultivation. [Copyright &y& Elsevier]