An attempt has been made to evaluate antimicrobial, antioxidant and cytotoxicity properties of extracts from onion (Allium cepa L.), garlic (Allium sativum), leaves of guava (Psidium guajava), papaya (Carica papaya), tea (Camellia sinensis), baen (Avicennia alba) and keora (Sonneratia apetala), respectively to apply as natural preservatives for tomatoes. The air-dried plant materials of the respective plant species were subjected to ethanol-methanol extraction, concentrated and stored at 4 °C before use. The extracts were dissolved in 95% ethanol for analysis of antioxidant and antimicrobial properties. Of the extracts tested, tea extracts showed the highest zone of inhibition against several pathogenic bacteria (E. coli 35.0±3.2 mm; P. aeruginosa 29.3±2.6 mm; S. typhi 28.4±2.1 mm and S. pyogenes 27.7±3.7 mm) using the disc diffusion method. In regard to DPPH free radical scavenging assay, keora and guava extracts showed the highest percentage of radical scavenging activity with the values of 89.64± 0.18 and 89.39± 0.88, respectively, which were in agreement with higher total antioxidant capacity (TAC) of these extracts obtained by the phosphomolybdenum method. Brine shrimp lethality bioassay for cytotoxicity assessment showed LC50 of 132.54 ± 18.99 µg/mL for the leaf extract of keora which was found to be most toxic among all studied extracts. The initial results indicated that the extracts could be used for food preservative applications based on the antimicrobial, antioxidant and cytotoxicity properties of the tested extracts. However, efficacy, stability and safety issues need to be addressed with both in vitro and in vivo studies.

The present research aimed to evaluate and compare the antioxidant activity in both pulp and peel and the physicochemical contents in the pulp of four local varieties of banana, i.e. Musa acuminata species named Sagor, Champa, Shail and Bichi, available in Sylhet region of Bangladesh. The antioxidant activity from a methanolic extract of banana peels and pulps was evaluated by determination of total phenolic content and DPPH scavenging activity. The physicochemical contents of banana pulp such as protein, fat, moisture, ash and carbohydrate were also determined. The results showed that the overall antioxidant activity of banana peel was higher than the pulp of banana. The pulp of the Shail variety had the highest antioxidant activity (TPC = 80.14 mg GAE/100 g, DPPH radical scavenging activity =91.37%) among the four varieties. Fat (1.38%) and moisture (76.23%) contents were higher in the pulp of Shail, while protein (1.82%) and carbohydrate (22.71%) contents were higher in the pulp of Bichi. The Champa variety contained higher ash content (1.05%). Among the jellies prepared from those banana varieties, the jelly of the Shail variety showed the highest score for overall acceptance (6.8) whilst the jelly prepared from the Bichi variety showed the highest score for taste (7.75). This may be due to higher carbohydrate content. The study suggests that banana peel could be used in the food industry as a raw material to produce bakery products and in cosmetics and pharmaceutical industries as an antioxidant supplement.