Primary, Secondary Metabolites, Biochemical and Antioxidant Activity of Orthosiphon staminues Benth (Misai Kucing) Under Cadmium Exposure

Aims: This study was conducted to evaluate the effects of cadmium (0, 3,6, 9 mg/kg) on the primary, secondary metabolites, biochemical and antioxidant activity in Orthosiphon stamineus.

Study Design: Orthosiphon stamineus seedlings were exposed to four levels of Cd (0, 3, 6 and 9 mg/kg) in the form of CdCl2 and were applied to the media during preparation. The experiment was organized in a randomized complete block (RCBD) design with three replications. Each experimental unit consisted of five seedlings, and there was a total of 135 seedlings used in the experiment.

Place and Duration of Study: Department of Biology, Faculty of Science Universiti Putra Malaysia between August 2013 to September 2013.

Methodology: Total soluble sugar and starch were determined spectrophometically using anthrone reagent, Total phenolics and flavonoid were determined using Folin-Ciocalteu reagent, hydrogen peroxide (H2O2) and lipid peroxidation were measured using potassium iodide (KI) and thiobarbiturate acid (TBA). The antioxidant activity was determined by DPPH reagent. Phenyll alanine lyase activity (PAL) was determined by using transcinnmic acid and cadmium determination by using inductively coupled plasma emission (ICPMS).

Results: Increased in Cd from 0 > 9 mg/kg, the production of total phenolics and flavonoid was enhanced in the shoot compared to the root parts. It was found that enhancement of total phenolics and total flavonoids might be contributed by enhancement of PAL and total non-structural carbohydrate (TNC) activity under cadmium exposure. Although total phenolic and total flavonoids increased, the antioxidant activity (DPPH) was reduced with high levels of Cd. It was also found that cadmium accumulated more in roots compared to the shoot. There was accumulation of H2O2 and lipid peroxidation as levels of Cd increased from 0 > 9 mg/kg indicating DNA damage under excess levels of cadmium. Total chlorophyll content also was reduced with increasing levels of cadmium indicating that cadmium disrupt nitrogen uptake of O. stamineus. The study showed that O. stamineus exposed to cadmium accumulate cadmium above the level recommended by WHO indicating there is a safety hazard when this plant is consumed for medicinal purposes.

Conclusion: The current study revealed that cadmium contamination would reduce the medicinal properties of O. stamineus although the production of secondary metabolites increased. This is explained by enhanced production of total phenolics, total flavonoids, but lower DPPH values.