Acid type impact on Sanrego (Lunasia amara Blanco) alkaloids using MAE, antibacterial, chemometric analysis

Sanrego (L. amara) is an endemic plant of South Sulawesi, renowned for its biological activities, including antioxidant, antimicrobial, antiparasitic, antidiabetic, and anticancer properties. This study aimed to identify the optimal acid solvent for extracting alkaloid compounds from L. amara stems and to evaluate the antibacterial activity of the resulting extracts. Alkaloid extraction was performed using Microwave Assisted Extraction (MAE) with various acid solvents, acetic acid, citric acid, tartaric acid, and hydrochloric acid at pH levels of 3, 4, and 5. The extracted compounds were analyzed by Thin Layer Chromatography-Densitometry (TLC-Densitometry), while antibacterial activity was assessed against Staphylococcus aureus and Escherichia coli. The results indicated that citric acid extraction at pH 5 yielded the highest alkaloid content, with an Area Under Curve (AUC) value of 29797.7. Chemometric analysis revealed outliers (EAT-pH5, EAS-pH3, EAT-pH3, EAA-pH3, and EAA-pH5) with unique chemical profiles that contribute substantially to the data variance and distribution. Extracts obtained using acid solvents at pH 5 demonstrated the strongest antibacterial activity against E. coli and S. aureus compared to those extracted at pH 3 and 4. Cluster analysis using Principal Component Analysis (PCA) indicated similar antibacterial activity among groups towards E. coli and S. aureus. It can be concluded that the Sanrego L. amara extract (EAS-pH5) contains the highest alkaloid content among the tested samples, and the acidic extract pH 5 has superior antibacterial activity.