Stability evaluations on Thunbergia laurifolia Lindl. leaf extract through HPLC, TLC and free radical scavenging activity analysis

Abstract

Regulatory guidelines recommend efficient stability studies on herbal products to establish their shelf lifes. In this study, dried extracts of Thunbergia laurifolia Lindl. leaves were subjected to three different storage conditions for six months: 1) 30 ± 2 ºC, 75 ± 5 % relative humidity (RH), 2) 40 ± 2 ºC, 75 ± 5 %RH, and 3) 2-8 ºC. Control and stability tested samples were evaluated for physical appearance, moisture content, caffeic acid and rosmarinic acid contents as chemical markers, and thin layer chromatography fingerprints, and determination for DPPH scavenging activity. Chemical marker contents and DPPH scavenging activities of the stability tested samples comparably retained with respect to the control samples after the storage for 3 months in all storage conditions. Pearson correlation analysis revealed the strong positive correlation between antioxidant activity and rosmarinic acid content of stability samples stored after 6 months with correlation coefficient (r) values more than 0.901 However, antioxidant activity was correlated positively with the caffeic acid content only stored after 3 months (r values less than 0.742). The results suggested that rosmarinic acid is more suitable to use as a chemical marker for evaluation of chemical and biological shelf lives of T. laurifolia leaf products.