Tyrosinase inhibitory study of flavonolignans from the seeds of Silybum marianum (Milk thistle).

Anti-melanogenesis effects of silymarin from milk thistle have been reported recently, but detailed tyrosinase inhibition properties of individual components have not been investigated. This study purported to substantiate tyrosinase inhibition and its mechanism based on a single metabolite. The responsible components for tyrosinase inhibition of target source were found out as flavonolignans which consist of isosilybin A (1), isosilybin B (2), silydianin (3), 2,3-dihydrosilychristin (4), silychristin A (5), silychristin B (6) and silybin (7), respectively. The isolated flavonolignans (1-7) inhibited both monophenolase (IC50 = 1.7-7.6 µM) and diphenolase (IC50 = 12.1-44.9 µM) of tyrosinase significantly. Their inhibitions were 10-fold effective in comparison with their mother skeletons (8-10). Inhibitory functions were also proved by HPLC analysis using N-acetyl-l-tyrosine as substrate. The predominant formation of Emet·I was confirmed from a long prolongation of lag time and a decrease of the static state activity of the enzyme. All tested compounds had a significant binding affinity to tyrosinase with KSV values of 0.06-0.27 × 104 L·mol-1, which are well correlated with IC50s. In kinetic study, all flavonolignan (1-7) were mixed type I (KI < KIS) inhibitors, whereas their mother skeletons (8-10) were competitive ones. The UPLC-ESI-TOF/MS analysis showed that the isolated inhibitors are the most abundant metabolites in the target plant.

Production of adventitious root biomass and secondary metabolites of Hypericum perforatum L. in a balloon type airlift reactor.

The effects of inoculum density, aeration volume and culture period on accumulation of biomass and secondary metabolites in adventitious roots of Hypericum perforatum in balloon type airlift bioreactors (3 l capacity) were investigated. The greatest increment of biomass as well as metabolite content occurred at an inoculum density of 3 g l(-1) and an aeration volume of 0.1 vvm. After 6 weeks of culture, an approximately 50-fold increase in biomass was recorded containing 60.11 mg g(-1) dry weight (DW) of phenolics, 42.7 mg g(-1) DW of flavonoids and 0.80 mg g(-1) DW of chlorogenic acid. Liquid chromatography-mass spectroscopy/mass spectroscopy demonstrated that the presence of quercetin and hyperoside in adventitious roots at a level of 1.33 and 14.01 µg g(-1) DW, respectively after 6 weeks of culture. The results suggest scale-up of adventitious root culture of H. perforatum for the production of chlorogenic acid, quercetin and hyperoside is feasible.

Polyozellin inhibits nitric oxide production by down-regulating LPS-induced activity of NF-kappaB and SAPK/JNK in RAW 264.7 cells.

Polyozellin, isolated from Polyozellus multiplex (Thelephoraceae), was investigated for its anti-inflammatory activity in the murine macrophage cell line RAW 264.7. Polyozellin inhibited both lipopolysaccharide (LPS)-induced nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) gene expression in a dose-dependent manner. The effects of polyozellin on the activation of nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein (MAP) kinases in these cells were studied in order to elucidate the underlying mechanism. Polyozellin suppressed the activation of both LPS-induced NF-kappaB and the stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), but had no effect on the extracellular signal-regulated kinase (ERK) or p38. These data suggest that polyozellin suppresses iNOS expression by inhibiting the activation of NF-kappaB and SAPK/JNK, leading to the inhibition of NO production.