Antibacterial and antioxidant activities of banana (Musa paradisiaca cv. Mysore) inflorescence, a banana by-product

• Main Author: Birdie Scott Padam
• Format: Thesis
• Language: English
• Published: 2012
• Online Access: https://eprints.ums.edu.my/id/eprint/18949/1/Antibacterial%20and%20antioxidant.pdf; https://eprints.ums.edu.my/id/eprint/18949/

Banana inflorescence (Musa paradisiaca cv. Mysore) was investigated for its potential bio-preservative activities, recycling an abundant agricultural by-product for higher value purposes. The study aims to extract antibacterials from the inflorescence and applying the selected extract fractions into food models. Extracts obtained using various solvent infusions were tested for antibacterial activity (agar-well diffusion, broth dilution) and antioxidant assays (DPPH, LPOI, TEAC, FRAP, TPC). Selected solvent was monitored under various extraction parameters (e. g. time, temperature and solvent%) prior to optimization using Response Surface Methodology (RSM) towards achieving the most efficient extraction procedure with the best antibacterial activity. Solid phase extraction (SPE) and liquid chromatography-mass spectrometry (UPLC/MS") were used to fractionate and elucidate antibacterial compounds within the selected extract fraction prior to application in food models as well as its cytotoxicity analysis using the brine shrimp lethality assay (BSLA). Notable antibacterial activity were observed (broth dilution) (MIC: 25.5 mg/ml - 42.0 mg/ml) from the methanolic extract against four susceptible food pathogen namely Staphylococcus aureus (SA), Bacillus cereus (BC), Listeria monocytogenes (LM) and Vbrio parahaemolyticus (VP). Optimization of extraction procedures (RSM) (time: 2.0 h, temperature: 40.1°C, methanol to water %: 90.1% v/v) significantly reduced the methanolic extract average MIC and MBC values by 21.9% and 14.2% respectively. Activity guided fractionation revealed antibacterial compounds such as epigallocatechin and its derivatives, benzoic acid derivative, xanthone derivative and 4 unknown nitrogen containing compounds. Methanolic-water fraction (H₂O Fr.) and SPE-fraction 3 (BS-F3) showed prominent antibacterial activity (MIC H₂O Fr.: 6.25 mg/mI - 28.0 mg/ml, MIC BS-F3: 0.63 mg/ml - 2.5 mg/ml) against SA, BC, LM and VP. EC50 values for DPPH and LPOI assays were 0.701 mg/ml and 0.755 mg/ml respectively for H₂O Fr. while BS-F3 showed remarkable values of 0.057 mg/ml and 0.059 mg/ml. BSF3 also exhibited high TEAC values (3.958 mmol TE/g extract), high FRAP values (4.362 mmol Fe ²⁺/g extract) with high TPC values (378.664 mg GAE/g extract). Decontamination of chicken breast meat using H₂O Fr. effectively suppressed the growth of LM for 7 consecutive days in both frozen (-18°C) and chilled (4°C) storage compared to the control. Meanwhile, BS-F3 incorporated into carrot juice eliminates BA and SA population to <1 log CFU/ml for 30 days in both chilled (4°C) and room temperature storage (25°C). Cytoxicity studies (BSLA) showed that H₂O Fr. and BS-F3 were potentially non-toxic (LD₅₀: 13.41 mg/ml and 5.41 mg/mI respectively). Thus, the banana inflorescence could be a promising source of natural bio-preservative to be applied in the food industry.