Variation of rhinacanthin content in Rhinacanthus nasutus and its health products.

Rhinacanthus nasutus has been traditionally used for skin infections, diabetes, inflammatory disorders and cancer therapies. Rhinacanthin-C, -D, and -N have been identified as its bioactive compounds. The content of active compounds in herbal raw materials and health products usually varies due to various factors, such as plant genetics, climate, and harvesting process. The present study aimed to determine the effect of harvesting factors, including part use and harvesting periods on rhinacanthin content of raw materials and health products of R. nasutus. Six parts of R. nasutus raw materials, i.e., leaves, flowers, roots, green twigs, brown twigs and aerial parts that separately harvested every two months together with two commercially available products of R. nasutus tea were extracted using a microwave-assisted extraction and subjected to quantitative HPLC analysis of rhinacanthin-C, -D, and -N. Among the plant parts, the roots contained the highest content of total rhinacanthins, followed by the leaves, in all every harvesting periods. While the other parts contained very low content of total rhinacanthins. In addition, the highest content of total rhinacanthins accumulated in roots (4.91 %, w/w) and leaves (4.42 %, w/w) were observed when they were harvested in September, while the lowest ones (3.73 % and 3.18 %, w/w, respectively) were found in March. In contrast, R. nasutus powders obtained from ten suppliers and two tea products contained very low content of total rhinacanthins and varied in the ranges of 0.14-0.55 %, w/w, which similar to those observed in the aerial part powders (0.27-0.53 %, w/w).