Seasonal variation of verbascoside as a principal phenolic compound linked with antioxidant potentials of Clerodendrum glandulosum Lindl. leaves

This study reports the influence of seasonality on the accumulation of verbascoside as a principal phenolic compound in Clerodendrum glandulosum Lindl. leaves along with possible alteration of antioxidant potentials. Leaves were collected during winter (December 2018), spring (February 2019), summer (May 2019), monsoon (July 2019), autumn (October 2019), and extracted with 95% aqueous methanol by cold maceration. The total phenolic content and antioxidant capacities (DPPH, ABTS and FRAP) were estimated by spectrophotometric technique, and verbascoside content was estimated by HPLC-PDA. Results indicate that the leaves collected during summer and winter both exhibited the highest total phenolic content verbascoside accumulation and antioxidant potentials which are significantly different (p < 0.05) than other seasons. Correlation studies further demonstrated that the total polyphenol and verbascoside contents were directly proportional to the antioxidant potentials. Thus, the study concludes that winter and summer are the best seasons for collecting leaves from this plant to obtain maximum antioxidant potential.