Characterization of Some Plant Extracts, Piperine, and Piperic Acid and Their Anti-Obesity and Anti-Acne Effects Through the In Vitro Inhibition of Pancreatic and Bacterial Lipases

Medicinal and culinary plants are identified as natural sources of antioxidants, bioactive molecules, and enzyme inhibitors, which are widely used for their nutritional and medicinal virtues. In attempts to identify natural extracts and molecules for overcoming obesity and acne issues, plant extracts of thyme (Thymus vulgaris), sage (Salvia officinalis), and ginger (Zingiber officinale) were prepared using solvents of different polarities. On the other hand, piperine was extracted from Piper nigrum with an extraction yield of 3.25 ± 0.12%. The piperic acid was obtained after the alkaline hydrolysis of piperine with a conversion rate of 97.2%. The ethanolic extract of ginger presented the highest radical scavenging activity with an IC50 = 17.3 ± 1.42 μg/mL, followed by the ethyl acetate extract of sage (IC50 = 20.16 ± 0.57 μg/mL). However, the ethyl acetate extract of ginger (IC50 = 27.87 μg/mL) presented the highest antioxidant activity with the β-Carotene-linoleic acid assay. Furthermore, only the ethanol and ethyl acetate extracts of sage, piperine, and piperic acid presented antibacterial activity against the B. subtilis strain. Using inhibition method A, 1 mg/mL ethyl acetate or ethanol extract of sage inhibited 94% or 79% of the chicken pancreatic lipase (CPL) activity, respectively. However, only 500 µg/mL of the same extracts or pure piperic acid completely inhibited the Staphylococcus xylosus lipase (SXL). Indeed, an IC50 of 54 ± 0.48 µg/mL and 68 ± 0.67 µg/mL were obtained with piperic acid and the sage ethyl acetate extract, respectively. Moreover, complete inhibition of SXL was obtained with piperic acid or ethanol extract of ginger, using inhibition method C, confirming the slight hydrophobic character of the inhibitors. Our results suggest that piperic acid and the studied ethanol/ethyl acetate extracts could play an important role as potent anti-obesity and anti-acne agents.