TLC-densitometric analysis of beta-sitosterol in agarwood leaf extracts

The leaves of agarwood (Aquilaria spp.) of Thymelaeaceae family, have been used as a herbal tea for health promotion. A quantitative TLC-densitometric method was developed and validated for determining of beta-sitosterol in leaf extracts of the three agarwood species i.e., Aquilaria crassna, A. malaccensis and A. subintegra, cultivated in Thailand. The method was validated for linearity, precision, accuracy, limit of detection (LOD) and limit of quantitation (LOQ). The linearity was found over the range of 125–1750ng/spot with r²=0.9996. The relative standard deviations of intraday and interday precisions studies were less than 2%. The average recovery was 100.78% while LOD and LOQ were 25 and 112.5ng, respectively. The contents of beta-sitosterol in the extracts of A. crassna, A. malaccensis and A. subintegra were 0.14, 0.12 and 0.12% w/w, respectively. The proposed TLC-densitometric method was simple, precise, specific, sensitive and accurate for routine quality control of raw materials of agarwood leaf extracts and their products.