Effect of harvesting age and drying condition on andrographolide content, antioxidant capacity, and antibacterial activity in Andrographis paniculata (Burm.f.) Nees

Quality of dried Andrographis paniculata (Burm.f.) Nees materials is important to determine its effectiveness in traditional medicine. The present study aimed to investigate an effect of harvesting age and drying condition on andrographolide content and its consequences on antioxidant and antibacterial activities. The plants were cultivated and harvested at 90,100,115, and 127 days after sowing (DAS) prior to drying under the sun or using hot air oven at 50, 65, and 80 ℃. The results indicated that drying condition significantly influenced andrographolide content, antioxidant capacities, and antibacterial activity of A. paniculata, whereas the harvesting age had no significant impact on those parameters. The andrographolide contents ranged from 0.74–4.11% (w/w) dry weight. The highest andrographolide contents were obtained at 90 DAS/65 ℃, 127 DAS/65 ℃, and 127 DAS/65 ℃. A. paniculata extracts were found to exhibit antibacterial activity against gram-positive bacterial strains (B. cereus, M. luteus, S. epidermidis, and S. aureus), which the highest antibacterial activity was observed at 90 DAS/65℃. The used of hot air oven at 65 ℃ effectively preserved andrographolide content and antibacterial activity of A. paniculata. In contrast, drying at 50 ℃ was the preferable drying condition for antioxidant capacity. The antioxidant activities of A. paniculata extracts ranged from 3.43–26.73 and 1.93–17.28 mg Trolox/g dry weight for DPPH• scavenging activity and FRAP reducing power activity, respectively. Overall, A. paniculata is suggested to dry using hot air oven at 65 ℃ to maintain high levels of andrograhpolide and antibacterial activity. Drying using hot air oven at 50 ℃ is advised, if antioxidant activity is the main focus. Even though the harvesting age is not a key parameter, A. paniculata is suggested to harvest at 50% flowering stage onward for a better total herbage and andrographolide yield.