Soursop leaves are a source of phytochemical compounds, such as phenolic acids, flavonoids, hydrolyzable tannins, and acetogenins. These compounds can have several types of biological activities. Lactic acid bacteria can uptake phenolic compounds present in plants or fruits. The aim of the present work was to investigate the in vitro effect of hexane, acetone, methanolic, and aqueous extracts of soursop leaves (Annona muricata L.) on the growth, motility, and biofilm formation of Lactobacillus casei, and to determine compounds related to growth. The minimum concentration promoting growth, motility (swimming, swarming, and twitching), and biofilm-forming capacity (crystal violet) were evaluated. The results showed the growth-promoting capacity of acetone and aqueous extracts at low doses 25–50 mg/L, and an inhibition in the four extracts at higher doses of 100 mg/L. The L. casei growth is related to ellagic acid, quercetin rhamnoside, kaempferol dihexoside, quercetin hexoside, secoisolariciresinol, and kaempferol hexoside-rhamnoside. Hexane extract increased the three types of motility, while aqueous maintained swimming and twitching motility similar to control. The four extracts inhibited the biofilm formation capacity.

This study aimed to evaluate the effect of noni (Morinda citrifolia L.) juice (NJ) in vitro and applied it to fresh-cut papaya to control Escherichia coli O157 : H7. Furthermore, the NJ effect on the physicochemical characteristics of fresh-cut papaya was evaluated. We determined the minimal inhibitory concentration (MIC) in a microplate reader by the microdilution method using TSB using an initial concentration of 1 × 10⁷ cells of E. coli/mL. Cubes of fresh-cut papaya fruit were immersed in an E. coli suspension (1 × 10⁵ cells/mL) and after that in NJ three times (0, 2.5, and 5 min) and then stored at 4 ± 1°C for 18 days. The presence of E. coli and total coliforms, as well as pH, TSS, and titratable acidity, were evaluated every three days. The results of in vitro assays showed that NJ at 20% inhibited the microbial growth of E. coli, finding a maximum growth rate (μmax) of −0.0066 h⁻¹. Immersion in NJ for 5 min presented a reduction of E. coli of 3.72 ± 1.43 log₁₀ CFU/ of fresh-cut papaya fruit treated with this bacteria on day 9 of storage regarding control. Likewise, fresh-cut papaya fruit immersed in NJ for 5 min maintained the total coliforms between 1 and -1 log₁₀ coliforms CFU/g for 18 days. However, the immersion treatment in NJ modified some physicochemical parameters of the fresh-cut papaya fruit, such as acidity and pH ( < 0.05). The application of NJ to fresh-cut papaya fruit showed in vitro and in vivo inhibition of E. coli and total coliforms, evidencing it as a possible bacterial control agent in the precut fruit industry for up to 18 days.