Evaluation of the Protective Effects of Chinese Herbs against Biomolecule Damage Induced by Peroxynitrite

A novel analytical method based on HPLC-PDA coupled post-column derivatization to evaluate the ability to inhibit tyrosine nitration in lotus leaf extracts

Protein tyrosine nitration plays a key role in many inflammatory and cardiovascular diseases and diabetes. Many natural products are used to treat these diseases through their ability to potentially interfere this reaction. Here, we describe a novel method to provide active fingerprinting of inhibition of tyrosine nitration by natural products based on post-column tyrosine nitration reaction analysis using high-performance liquid chromatography coupled to a photometric diode array. Results indicated that lotus leaf extracts exhibited obvious inhibitory activity against tyrosine nitration by peroxynitrite, and that chemical and active fingerprints were simultaneously established, with the active fingerprints indicating the active compounds of the lotus leaves. Additionally, flavonoids were screened as the principal active compounds involved in inhibiting tyrosine nitration in the lotus leaf extracts, with quercetin-3-O-glucuronide and quercetin-3-O-glucoside exhibiting the greatest contributions. Moreover, our results suggested that lotus leaves from three regions (Nanjing, Suzhou, and Hangzhou) exhibited the best inhibitory activity. These findings indicated the usefulness of this method for screening active compounds involved in inhibiting protein tyrosine nitration, and that similar strategies can likely be applied to evaluate the inhibitory activity against tyrosine nitration of other natural products.

A novel analytical method based on HPLC-PDA coupled post-column derivatization to evaluate the inhibitory activity of tyrosine nitration in lotus leaf extracts.

Biological activity of clovers - free radical scavenging ability and antioxidant action of six Trifolium species

CONTEXT

Clovers were chosen on the basis of traditional medicine recommendations, agricultural value, or available information on their promising chemical profiles.

OBJECTIVE

This study evaluates and compares free radical scavenging and antioxidant properties of six clover species: Trifolium alexandrinum L. (Leguminosae), Trifolium fragiferum L., Trifolium hybridum L., Trifolium incarnatum L., Trifolium resupinatum var. majus Boiss., and Trifolium resupinatum var. resupinatum L.

MATERIALS AND METHODS

Free radical scavenging activity of the extracts (1.5-50 µg/ml) was estimated by reduction of 1,1-diphenyl-2-picrylhydrazyl (DPPH(•)) and 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic) acid (ABTS(•)) radicals. The Trifolium extract effects on total antioxidant capacity of blood plasma were determined by the reduction of ABTS(•+) and DPPH(•) radicals, as well as with the use of the ferric reducing ability of plasma (FRAP) assay.

RESULTS

The UPLC analysis of chemical profiles of the examined extracts showed the presence of three or four groups of phenolic substances, including phenolic acids, clovamides, isoflavones, and other flavonoids. The measurements of free radical scavenging and ferric reducing ability of the examined clover extracts revealed the strongest effect for T. alexandrinum. Furthermore, antioxidant activity assays in human plasma have shown protective effects of all extracts against peroxynitrite-induced reduction of total antioxidant capacity.

CONCLUSIONS

Trifolium plants may be a rich source of bioactive substances with antioxidant properties. The examined extracts displayed free radical scavenging action and partly protected blood plasma against peroxynitrite-induced oxidative stress; however, the beneficial effects of T. alexandrinum and T. incarnatum seem to be slightly higher.