The development of callus and cell suspension cultures of Sabah Snake Grass (Clinacanthus nutans) for the production of flavonoids and phenolics

Abstract

Clinacanthus nutans (Burm.f.) Lindau is a valuable medicinal plant that has gained interest as a side treatment for cancer in Southeast Asia. Phenolic and flavonoid compounds identified in this plant have been linked to anti-cancer properties. However, quantification of such metabolites in plants varies depending on cultivation methods and conditions resulting in inconsistent yield. This study aims to establish cell suspension culture of C. nutans, evaluate the accumulation of phenolics, flavonoids and to assess the antioxidant activity of extracts from in vitro cultures. Callus was induced from leaf explants of C. nutans and proliferated on Murashige & Skoog (MS) medium supplemented with different combinations of plant growth regulators (2,4-dichlorophenoxyacetic acid, 6-benzylaminopurine and kinetin). Assessment of growth kinetics for the suspension culture was performed. The total phenolic, flavonoid contents and antioxidant activity of the extracts were evaluated followed by high-performance liquid chromatography (HPLC) to detect selected flavonoids. MS medium supplemented with 0.25 mg/L 2, 4-D and 0.25 mg/L BAP was optimal for callus induction, proliferation and suspension cultures. The highest total phenolic content was obtained from suspension cells (55.35 mg GAE/g DW) whereas leaf showed the highest flavonoid content (25.13 mg QE/g DW). Leaf extract demonstrated the strongest antioxidant activity with the lowest IC50 value (117.42 μg/mL). HPLC analysis revealed the presence of catechin, luteolin, quercetin and kaempferol in the suspension cells and the leaf. The present study indicated that cell suspension cultures are able to accumulate higher phenolic compounds and possess all four selected flavonoids similar to the outdoor grown plant.