Portable, Rapid, and Cost-Effective Smartphone-Based Colorimetric Quantification of Total Lactones in Andrographis paniculata

Background/Objectives: Andrographis paniculata is listed in the Thai National List of Essential Medicines. The Thai Herbal Pharmacopoeia specifies the required contents of total lactones and andrographolide for the quality control of the aerial parts of A. paniculata. Effective pre-harvest quality control throughout the cultivation period is essential to ensure compliance with these quality standards. In this study, we aimed to develop a portable smartphone-based colorimetric method for the determination of total lactone content, thereby facilitating in-field quality control of A. paniculata raw materials. Methods: Methanol was used as the extraction solvent, and the analytes were extracted using a simple procedure derived from the United States Pharmacopeia concept. The colorimetric reaction was based on a charge-transfer reaction between the α,β-unsaturated γ-lactone moiety and 3,5-dinitrobenzoic acid, producing a red-purple product in a microwell plate. The delta-green intensity of the reaction product was captured as an andrographolide equivalent using a smartphone camera and quantified through digital image processing with a custom-developed mobile application. Results: A linear working range of 15–100 µg/mL was exhibited with limits of detection and quantification of 4.9 and 15.0 µg/mL, respectively. The practical applicability of the developed method was evaluated using A. paniculata samples and compared with the conventional spectrophotometric method. The results showed excellent agreement between the two methods, with a correlation coefficient of 0.9986. Conclusions: The results of this study suggest that this portable and rapid method is feasible for in-field/on-site analysis to facilitate pre-harvest quality control throughout the cultivation period, ensuring that harvested A. paniculata materials comply with established quality standards for plant-derived natural active pharmaceutical ingredients (NAPIs). The proposed method has the potential to promote sustainable production and responsible resource utilization by improving the quality of herbal raw materials intended for the manufacture of herbal medicines and dietary supplements, in line with UN-SDG #12 and #3.