Anti-inflammatory and antioxidant activities of red pepper (Capsicum annuum L.) stalk extracts: Comparison of pericarp and placenta extracts

Red pepper stalks, an agricultural waste product, are casually discarded at landfills where they oxidize and harm the local ecology. To our knowledge, no feasible method has been designed to evaluate the bioavailability of red pepper stalks. Therefore, the present study focused on the stalk waste investigating its superoxide dismutase (SOD) activity and inhibitory effect on nitric oxide (NO) production in macrophages. Interestingly, by comparison with red pepper pericarp and placenta extracts, the stalks were found to have higher phenolic, flavonoid, and capsaicin contents. Chromatographic data showed differences in the amounts of phenolic compounds in various parts of red pepper. At a concentration of 100 μg/mL, the stalk, placenta, and pericarp had SOD activities of 52.3%, 7.4%, and 10.4%, respectively. A very high level of chlorogenic acid (3.82 mg/g d w) and p-coumaric acid (2.98 mg/g d w) gave the stalks of red peppers the most powerful antioxidant activity among the three tested parts. The high phenolic and SOD activity-containing stalks also had the most significant NO inhibitory effect (53.5%) in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells. These results demonstrated that there is an opportunity to develop a new anti-inflammatory agent from agricultural wastes.