Flavonoids, a Potential New Insight of Leucaena leucocephala Foliage in Ruminant Health.

We investigated the constituents of Leucaena leucocephala foliage collected from Guangdong province in China and isolated 17 diverse flavonoids (1-17), including flavones (5-9, 11, and 12), flavonols (1, 10, and 16), flavanone 4, flavanonol 15, and flavonol glycosides (2, 3, 13, 14, and 17). Flavonoids quercetin (1), quercetin-3- O-α-rhamnopyranoside (2), and myricetin-3- O-α-rhamnopyranoside (17) were the major flavonoids components in L. leucocephala leaves, at a total concentration of about 2.5% of dry matter. pHRE-Luc inductive activity to mimic the activation of erythropoietin (EPO) gene, anti-inflammatory, antidiabetic, and antioxidant activities of isolated flavonoids (1-17) were evaluated. Flavonoids 7, 10, and 13 could strongly induce the transcriptional activity of pHRE-Luc, which indicated their potential to induce the expression of EPO. Flavonoids 7, 10, 13, and 17 displayed strong anti-inflammatory activity, relatively equal to the positive control dexamethasone. Flavonoids 1, 2, 3, 11, 12, 16, and 17 showed stronger antioxidant activities of DPPH radical scavenging capacity than ascorbic acid. Flavonoids 1, 2, and 10 showed weak cellular antioxidant activities against tert-butyl hydroperoxide (tBHP) induced ROS formation. Flavonoid rhamnoside 2 and arabinoside 3 undergone deglycosylation to the aglycone quercetin under anaerobic incubation with cattle rumen microorganisms. Furthermore, the potential health benefits for ruminant of flavonoids, which was rich in L. leucocephala foliage, was also discussed.

Jasmonate-Elicited Stress Induces Metabolic Change in the Leaves of Leucaena leucocephala.

The plant Leucaena leucocephala was exposed to four jasmonate elicitors, i.e., jasmonic acid (JA), methyl jasmonic acid (MeJA), jasmonoyl-l-isoleucine (JA-Ile) and 6-ethyl indanoyl glycine conjugate (2-[(6-ethyl-1-oxo-indane-4-carbonyl)-amino]-acetic acid methyl ester) (CGM). The treatment was to mimic the herbivores and wounding stresses. By using NMR spectroscopy along with chemometric analysis, including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), the changes of metabolites in the leaves of L. leucocephala were determined under the stress as induced by the four elicitors. The challenge of JA-Ile caused an accumulation of lactic acid (6), ß-glucose (10), alanine (12), threonine (13), steroids (18), 3,4-dihydroxypyridine (19) and an unidentified compound 20. The chemometric analysis of the PCA and PLS-DA models indicated that the alternation of metabolites triggered by JA, MeJA, and CGM treatments were very minimum. In contrast, the treatment by JA-Ile could induce the most significant metabolic changes in the leaves. Moreover, there was very minimal new metabolite being detected in responding to the jasmonate-induced stresses. The results showed some metabolite concentrations changed after application of the elicitors, which may be related to a high level of tolerance to stress conditions as well as the strong ecological suitability of L. leucocephala.

Synthesis of prenylated flavonols and their potents as estrogen receptor modulator.

Prenylated flavonols are known as phytoestrogen and have good bioactivties. However, their abundances in nature are pretty low. It is required to find an efficient synthesis technique. Icariin is a prenylated flavonol glycoside with low cost. It can be used to synthesize different prenylated flavonols. A combination of cellulase and trifluoacetic acid hydrolysis could effectively remove rhamnose and glucose from icariin. Icaritin, anhydroicaritin and wushanicaritin were the leading prenylated flavonol products. Their affinities to estrogen receptors α and ß were predicted by docking study. The weak affinity of wushanicaritin indicated that prenyl hydroxylation impaired its affinity to estrogen receptor ß. The prenyl cyclization led to a loss of affinity to both receptors. The interactions between icaritin and ligand binding cavity of estrogen receptor ß were simulated. π-π stacking and hydrophobic forces were predicted to be the dominant interactions positioning icaritin, which induced the helix (H12) forming an activated conformation.