Deactivation of ferrylmyoglobin by vanillin as affected by vanillin binding to β-lactoglobulin

Recent Research Progress: Discovery of Anti-Plant Virus Agents Based on Natural Scaffold

Plant virus diseases, also known as “plant cancers”, cause serious harm to the agriculture of the world and huge economic losses every year. Antiviral agents are one of the most effective ways to control plant virus diseases. Ningnanmycin is currently the most successful anti-plant virus agent, but its field control effect is not ideal due to its instability. In recent years, great progress has been made in the research and development of antiviral agents, the mainstream research direction is to obtain antiviral agents or lead compounds based on structural modification of natural products. However, no antiviral agent has been able to completely inhibit plant viruses. Therefore, the development of highly effective antiviral agents still faces enormous challenges. Therefore, we reviewed the recent research progress of anti-plant virus agents based on natural products in the past decade, and discussed their structure-activity relationship (SAR) and mechanism of action. It is hoped that this review can provide new inspiration for the discovery and mechanism of action of novel antiviral agents.

Riboflavin photosensitized oxidation of myoglobin

The reaction of the fresh meat pigment oxymyoglobin, MbFe(II)O₂, and its oxidized form metmyoglobin, MbFe(III), with triplet-state riboflavin involves the pigment protein, which is oxidatively cleaved or dimerized as shown by SDS-PAGE and Western blotting. The overall rate constant for oxidation of MbFe(II)O₂ by ³Rib is (3.0 ± 0.5) × 10⁹ L·mol⁻¹·s⁻¹ and (3.1 ± 0.4) × 10⁹ L·mol⁻¹·s⁻¹ for MbFe(III) in phosphate buffer of pH 7.4 at 25 °C as determined by laser flash photolysis. The high rates are rationalized by ground state hydrophobic interactions as detected as static quenching of fluorescence from singlet-excited state riboflavin by myoglobins using time-resolved fluorescence spectroscopy and a Stern-Volmer approach. Binding of riboflavin to MbFe(III) has K(a) = (1.2 ± 0.2) × 10⁴ mol·L⁻¹ with ΔH° = -112 ± 22 kJ·mol⁻¹ and ΔS° = -296 ± 75 J·mol⁻¹·K⁻¹. For meat, riboflavin is concluded to be a photosensitizer for protein oxidation but not for discoloration.

Reduction of ferrylmyoglobin by theanine and green tea catechins. Importance of specific Acid catalysis

Reduction of the hypervalent heme pigment ferrylmyoglobin by green tea catechins in aqueous solution of pH = 7.5 was investigated by stopped-flow spectroscopy. Reduction by the gallic acid esters epigallocatechin gallate (EGCG, k2 = 1460 L mol(-1) s(-1), 25.0 °C, 0.16 ionic strength) and epicatechin gallate (ECG, 1410 L mol(-1) s(-1)) was found faster than for epicatechin (EC, 300 L mol(-1) s(-1)) and epigallocatechin (EGC, 200 L mol(-1) s(-1)), even though the gallate ion (G, 330 L mol(-1) s(-1)) is similar in rate to EC. The rate for reduction by EC, EGC, ECG, EGCG, and G shows no correlation with their oxidation potentials or phenolic hydrogen-oxygen bond dissociation energy, but with the pKa of the most acidic phenol group. Theanine, with an acidity similar to that of EC, reduces ferrylmyoglobin with a similar rate (200 L mol(-1) s(-1)), in support of general acid catalysis with an initial proton transfer prior to electron transfer.