5-hydroxytryptophan (5-HTP) is an important substance thought to improve depression. It has been shown that Lactobacillus can promote the secretion of 5-HTP in the body and thus ameliorate depression-like behavior in mice. However, the mechanism by which Lactobacillus promotes the secretion of 5-HTP is unclear. In this study, we investigated the promoting effect and mechanism of Lactobacillus, isolated from Chinese fermented foods, on the secretion of 5-HTP. The results showed that Lactobacillus (L.) pentosus LPQ1 exhibited the strongest 5-HTP secretion-promoting effect ((9.44 ± 0.69)-fold), which was dependent on the mixture of compounds secreted by L. pentosus LPQ1 (termed SLPQ1). In addition, the results of the RNA sequencing (RNA-seq) and quantitative real-time polymerase chain reaction (qRT-PCR) analyses indicated that SLPQ1 alters the TNF and oxidative phosphorylation signaling pathways. Moreover, the SLPQ1 ultrafiltration fraction (>10 kDa) showed a similar 5-HTP promoting effect as SLPQ1. Furthermore, reverse-phase liquid chromatography-tandem mass spectrometry (RPLC-MS/MS) identified 29 compounds of >10 kDa in SLPQ1, including DUF488 domain-containing protein, BspA family leucine-rich repeat surface protein, and 30S ribosomal protein S5, which together accounted for up to 62.51%. This study reports new findings on the mechanism by which L. pentosus LPQ1 promotes 5-HTP production in some cell lines in vitro.
The in vitro and in vivo antioxidant activities of six flavonoids with similar structures, including epicatechin (EC), epigallocatechin (EGC), procyanidin B2 (P), quercetin (Q), taxifolin (T), and rutin (R) were compared. The structures of the six flavonoids and their scavenging activities for 2,2-diphenyl-1-picrylhydrazyl (DPPHâ¢) and 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS+) radicals were closely related. The flavonoids decreased serum contents of malondialdehyde (MDA) and nitric oxide (NO), and increased serum total antioxidative capacity (T-AOC), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) levels to different degrees in d-galactose-treated mice. The changes in mRNA expression of liver GSH-Px1, CAT, SOD1, and SOD2 by d-galactose were dissimilarly restored by the six flavonoids. Moreover, the six flavonoids differentially prevented the inflammatory response caused by oxidative stress by inhibiting interleukin (IL)-1ß, IL-6, and tumor necrosis factor (TNF)-α levels, and restoring IL-10 levels. These six flavonoids from two subclasses revealed the following antioxidant capability: P > EC, EGC > EC, Q > T, Q > R. Our results indicate that (1) the pyrogallol, dimerization, and C2=C3 double bonds of flavonoids enhanced antioxidant activity and (2) the C3 glycosylation of flavonoids attenuated antioxidant capacity.
