Exploring the effectiveness of phenolic antioxidants extracted from Annona muricata L. fruit seeds and peel using ultrasound-assisted extraction

Abstract

Utilizing antioxidants from fruit by-products promote sustainability in food industry by reducing waste. This study investigated the effectiveness of ultrasound-assisted extraction in extracting phenolic antioxidants from Annona muricata L. fruit seeds (ASE) and peel (APE), determining the total phenolic content (TPC), total flavonoid content (TFC), phytochemical composition, antioxidant activity, and antibacterial activity. Phenolic antioxidants were extracted using 100% ethyl acetate using both vortex-mixed and ultrasound-assisted extractions. TPC and TFC were determined using Folin-Ciocalteu’s method and Aluminium Chloride colorimetric method respectively. Gas chromatography-mass spectrometry (GC–MS) analysis was performed to identify the phytochemicals present in extracts. Antioxidant activity of the extracts was evaluated using ABTS+ radical scavenging assay and compared with synthetic antioxidants; butylated hydroxytoluene (BHT) and butylated hydroxyl anisole (BHA). Antibacterial activity against food-borne pathogens Staphylococcus aureus and Salmonella typhi was assessed by measuring the inhibition zone diameter via the disc diffusion method. Results indicated that ultrasound-assisted extracts resulted significant (p<0.05) increase of TPC of ASE in 41% and APE in 48%, and TFC by 8% for both ASE and APE than vortex-mixed extracts. GC-MS analysis identified 1,2,3-Propanetriol, 9-Octadecenoic acid, n-Hexadecanoic acid in ASE and 1,2,3-Propanetriol, Oleic Acid, n-Hexadecanoic acid in APE as major phytochemicals. Half- maximal inhibitory concentration (IC50 μg/mL) of ultrasound-assisted extracts of ASE and APE was 29±0 and 42±1 respectively compared to BHT (63±1) and BHA (97±1) while vortex-mixed extracts resulted 49±0, 55±0 respectively. Ultrasound-assisted extracts of ASE (9±1, 8±0mm) and APE (7±1, 7±0mm) showed higher inhibition against Staphylococcus aureus and Salmonella typhi. Respectively than vortex-mixed extracts of ASE and APE (8±0, 0±0 and 6±0, 6±0 mm respectively), while synthetic antioxidants showed zero inhibitory effect and therefore, they lack antibacterial activity. Ultrasound- assisted method is a potential extraction technique, and the tested natural sources could be promising alternatives to synthetic antioxidants due to their increased antioxidant and antibacterial activities.