Litchi pulp-derived gamma-aminobutyric acid (GABA) extract counteracts liver inflammation induced by litchi thaumatin-like protein.

Gamma-aminobutyric acid (GABA) is the predominant amino acid in litchi pulp, known for its neuroregulatory effects and anti-inflammatory properties. Although previous research has highlighted the pro-inflammatory characteristics of litchi thaumatin-like protein (LcTLP), interplay between GABA and LcTLP in relation to inflammation remains unclear. This study aims to explore the hepatoprotective effects of the litchi pulp-derived GABA extract (LGE) against LcTLP-induced liver inflammation in mice and LO2 cells. In vivo experiments demonstrated that LGE significantly reduced the levels of aspartate transaminase and alanine transaminase, and protected the liver against infiltration of CD4+ and CD8+ T cells and histological injury induced by LcTLP. Pro-inflammatory cytokines including interleukin-6, interleukin-1ß, and tumor necrosis factor-α were also diminished by LGE. The LGE appeared to modulate the mitogen-activated protein kinase (MAPK) signaling pathway to exert its anti-inflammatory effects, as evidenced by a reduction of 47%, 35%, and 31% in phosphorylated p38, JNK, and ERK expressions, respectively, in the liver of the high-dose LGE group. Additionally, LGE effectively improved the translocation of gut microbiota by modulating its microbiological composition and abundance. In vitro studies have shown that LGE effectively counteracts the increase in reactive oxygen species, calcium ions, and pro-inflammatory cytokines induced by LcTLP. These findings may offer new perspectives on the health benefits and safety of litchi consumption.

Postharvest quality maintenance of wax apple and guava fruits by use of a fermented broth of an ε-poly-l-lysine-producing Streptomyces strain.

ε-Poly-l-lysine (ε-PL) is a natural antimicrobial polymer with significant inhibitory activity against a broad spectrum of microorganisms, and nowadays used widely as a preservative in the food industry. In the present study, ε-PL broth was obtained from Streptomyces ahygroscopicus GIM8 fermentation in a nutrient-limited liquid medium. The in vitro antifungal activity of the broth against fruit pathogens Penicillium expansum and Colletotrichum gloeosporioides was investigated, and its usage for postharvest storage of two highly perishable fruits wax apple and guava was evaluated. Results showed that ε-PL concentration in the broth reached 0.61 g/L, and the nutrition level of the broth was low. The antifungal activity of ε-PL broth was comparable to that of the aqueous solution of ε-PL under the same concentration. Immersion with the diluted broth (200 mg/L ε-PL) markedly delayed the decline in the quality of postharvest wax apple and guava fruits during storage, and the decay incidences were also greatly decreased as compared to their respective controls (distilled water immersion). A further investigation demonstrated that the ε-PL broth immersion induced an increase in the activity of defense-related enzymes peroxidase and polyphenol oxidase in the two fruits during storage. The present study proved that the fermentation broth of ε-PL could be used as a promising alternative to high purity ε-PL and synthetic fungicides for preserving fruits at postharvest stage.