Effects of growth regulators on production of bioactive compounds from Clinacanthus nutans (Burm.f.) Lindau "Phaya Yo" culture in vitro

Clinacanthus nutans is a valuable plant that is harvested for medicinal purposes in Southeast Asia. However, the production of herbal medicines needs raw, uncontaminated materials with a consistent quantity of bioactive compounds. Therefore, in vitro culture is of interest for the production of secondary metabolites. The present study applied plant growth regulators to stimulate bioactive compounds from multiple shoots of Clinacanthus nutans. Nodal explants were studied for multiple shoot induction using different types of plant growth regulators: thidiazuron (TDZ) alone or in combination with 1-naphthaleneacetic acid (NAA). The obtained calli or multiple shoots were examined for bioactive compounds (total phenolic, flavonols/flavones, phytosterols and antioxidant activity). The results showed that TDZ at concentrations of 0.5-1.0 mg/l either alone or in combination with NAA at concentrations of 0.01-0.1 mg/l stimulated a higher total phenolic content (including antioxidant activity) than the control. At such concentrations, TDZ and NAA were more likely to stimulate lupeol production in the tissue and its content was higher than in the leaves from the pot-grown plants. The present result revealed suitable growth regulator factors for stimulating the production of bioactive compounds, such as total phenolic compounds, antioxidants and phytosterols and especially lupeol, which were found in the tissues of C. nutans at a level 98.25-folds higher than in the leaves from the pot-grown plants. This technique could support the production of raw materials containing known quantities of various bioactive compounds at the laboratory level and be used for further research on the creation of quantitative bioactive compounds in C. nutans herbs for commercial production.