Antioxidant and apoptotic activity of cocoa bean husk extract on prostate cancer cells

Background: Although prostate cancer is the most commonly diagnosed cancer in men, its incidence among Asians, who consume foods rich in phenols, is relatively low compared with that in other populations. Cocoa bean husk (CBH) is an important by-product of the cocoa industry; its polyphenol content (catechin, epicatechin, and procyanidin B) is as high as that of cocoa beans. However, there are no studies on the anticancer effect of CBH. Herein, we assessed the antioxidant and anticancer effects of CBH on prostate cancer cells. Objectives: We fractionated CBH ethanol crude extract and compared the total polyphenol content, total flavonoid content, and DPPH and ABTS⁺ radical scavenging activities of the fractions. Catechin, epicatechin, and procyanidin B were analysed by HPLC in the ethyl acetate (EAF) and butanol (BF) fractions, which had the highest physiological content and antioxidant activity. PC3 and DU145 cells were treated with the two fractions, and annexin V/propidium iodide, and TUNEL assays were performed to assess apoptosis and DNA fragmentation, respectively. Results: The highest phytochemical content and antioxidant activity were observed in EAF, followed by those in BF. HPLC analysis revealed high content of phenolic compounds in both these fractions. Notably, catechin (5.64 mg/g), epicatechin (20.47 mg/g), and procyanidin B (20.29 mg/g) were abundant in EAF. Both fractions induced apoptosis in a concentration-dependent manner in PC3 and DU145 cells, and DNA fragmentation at a concentration of 200 μg/mL. Conclusion: CBH, a by-product of cocoa processing, contains large amounts of phenolic compounds and exhibits high antioxidant activity and anticancer effects on prostate cancer cells. CBH has potential applications as a functional food material.