Thermal degradation kinetics of andrographolide, 14-deoxy-11,12-didehydroandrographolide and neoandrographolide extracted from Andrographis paniculata’s plant at different temperature

Extraction is a commonly used technique to obtain plant's bioactive compounds. However, the aforementioned technique involved prolonged thermal exposure which can cause a degradation of bioactive compounds. Thus, this paper presents a degradation kinetics study of terpene markers from Andrographis paniculata extracts. The degradation of terpenes occurs at elevated temperature during the herbal processing such as extraction and spray drying. In the present study, the effect of heating at temperature ranging from 100 to 150 °C for 90 minutes on the terpene content was studied. The heated and unheated A. paniculata extracts was analyzed using an ultra-performance liquid chromatography to quantify the terpene content. It was observed that terpenes degrade into smaller fragments during heating as such andrographolide degrades to form 14-deoxy-11,12-didehydroandrographolide. All the three terpenes marker follows the zero-order kinetics during thermal degradation. Generally, the total amount of andrographolide, 14-deoxy-11,12-didehydroandrographolide and neoandrographolide reduced by 79.55, 76.00 and 75.68%, respectively after the thermal exposure at 100 °C. All the studied terpenes are prone to degradation upon exposure to heat above 100 °C.