Application of Deep Eutectic Solvents to Kleinhovia hospita L.: Total Flavonoid Content and Anti-cholesterol Activity

Hypercholesterolaemia is a major risk factor for cardiovascular disease. Tahongai (Kleinhovia hospita L.) leaves contain flavonoids with potential cholesterol-lowering activity. This study aimed to determine the total flavonoid content, evaluate the anti-cholesterol activity, and analyse the relationship between both parameters in Kleinhovia hospita L. leaves extracts obtained by Ultrasound-Assisted Extraction (UAE) using Deep Eutectic Solvents (DES) composed of propylene glycol and lactic acid. This experimental study employed DES propylene glycol-lactic acid at three molar ratios (1:1, 1:2, and 2:1). Total flavonoid content was determined using the aluminium chloride colourimetric method with UV–Visible spectrophotometry, while anti-cholesterol activity was evaluated in vitro using the Liebermann–Burchard method, with simvastatin as the positive control. The highest total flavonoid content was found in the DES propylene glycol-lactic acid molar ratio of 2:1, with a value of 679.99 mg QE/g. At 25 µg/mL, the highest cholesterol inhibition was observed at a molar ratio of 2:1 (45.73%), whereas simvastatin showed 89.47% inhibition. Pearson analysis revealed a very strong negative correlation between total flavonoid content and anti-cholesterol activity (r=−0.997; p=0.050). The DES propylene glycol-lactic acid at a molar ratio of 2:1 yielded the highest total flavonoid content and the strongest anti-cholesterol activity.