Cui Ping Chen

Study on the inhibitory effect of tannins and flavonoids against the 1,1-diphenyl-2-picrylhydrazyl radical

Fifty-one tannins and forty-one flavonoids isolated from Oriental medicinal herbs were evaluated for their antioxidant ability with a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-generating system. The results showed that tannins and certain flavonoids are potential free-radical scavengers, and that their activity against the DPPH radical is closely associated with their chemical structure. A comparison of the two classes of compounds showed that tannins have more potential than flavonoids because almost all the tannins demonstrated significant scavenging action within a low concentration range, whereas the activity of flavonoids varied distinctively among the different compounds. An increase of galloyl groups, molecular weight, and ortho-hydroxyl structure enhanced the activity of tannins, whereas the number and position of hydroxyl groups were important features for the scavenging of free radicals by flavonoids. Moreover, it appeared that when the free hydroxyl group was methoxylated or glycosylated, the inhibitory activity was obviously decreased or even abolished.

Inhibitory effect of caffeic acid analogues isolated from Salviae miltiorrhizae Radix against 1,1-diphenyl-2-picrylhydrazyl radical

Caffeic acid and its four polymers isolated from Salviae Miltiorrhizae Radix were examined for their activity of scavenging free radicals in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical generating system. The results showed that the polymers of caffeic acid inhibited the DPPH radical more strongly than caffeic acid. The strongest activity was displayed by two tetramers, lithospermic acid B and its Mg2+ salt. The trimer (lithospermic acid) and dimer (rosmarinic acid) showed similar efficiency. In comparison, caffeic acid was less efficient in scavenging free radicals. Determination of the activity of caffeic acid derivatives of small molecules revealed that the o-dihydroxyl group was the most important active structure of caffeic acid derivatives for scavenging of free radicals. Lack or substitution of this structure resulted in marked reduction or even loss of the activity. Structural modification of the side chain of caffeic acid produced slight changes in activity. The present results demonstrate that a saturated group connected to the aromatic ring has slightly higher inhibitory activity against the DPPH radical than an unsaturated group.

Protective effects of Glycyrrhizae radix extract and its compounds in a renal hypoxia (ischemia)-reoxygenation (reperfusion) model.

Glycyrrhizae radix water extract (GRWE) and its two major constituents glycyrrhizin and 3-glycyrrhetinic monodesmoside, significantly suppressed LDH leakage and MDA release, whereas glycyrrhetinic acid had no effect. On the other hand, in rats subjected to ischemia-reperfusion, the activities of endogenous antioxidant enzymes including catalase and glutathione peroxidase showed recovery, whereas the levels of urea nitrogen and creatinine in serum were reduced by administration of glycyrrhizin orally for 30 days prior to ischemia-reperfusion. These results indicate that GRWE and its two constituents may be promising for amelioration of hypoxia (ischemia)-reoxygenation (reperfusion) injury and improvement of renal function by acting directly or indirectly as antioxidant and oxygen radical-scavenging agents.

Direct scavenging of nitric oxide by traditional crude drugs.

Thirty-one traditional crude drugs and several pure compounds were examined for their possible regulatory effect on nitric oxide (NO) levels using sodium nitroprusside as a NO donor in vitro. Most of the crude drugs tested demonstrated direct scavenging of NO. Eight crude drugs, including Sanguisorbae Radix, Caryophylli Flos, Gambir, Coptidis Rhizoma, Granati Cortex, Gallae Rhois, Rhei Rhizoma and Cinnamomi Cortex exhibited significant activity (IC50 values < 1000 micrograms/ml), and with the exception of Coptidis Rhizoma, all were found to contain tannins as their major constituents. In addition, some crude drugs containing flavonoids or essential oils also appeared to act against NO. Ten major tannins contained in Sanguisorbae Radix and Rhei Rhizoma showed high scavenging activity (IC50 values < 326.3 micrograms/ml), and 6 of 8 alkaloids obtained from Coptidis Rhizoma also effectively scavenged the NO radical (IC50 values < 455.4 micrograms/ml). It was indicated that these compounds may be the active principles of the crude drugs responsible for NO scavenging. The present results suggest that traditional crude drugs might be potent and novel therapeutic agents for scavenging of NO and the regulation of pathological conditions caused by excessive NO and its oxidation product, peroxynitrite. These findings may also help to explain, at least in part, certain pharmacological activities of crude drugs, especially anti-infection and anti-inflammatory activities.

Potential of Sanguiin H-6 against Oxidative Damage in Renal Mitochondria and Apoptosis Mediated by Peroxynitrite in vivo

Potential of sanguiin H-6, a component of Sanguisorbae Radix, to protect against oxidative damage in renal mitochondria and apoptosis mediated by peroxynitrite (ONOO–) was examined using a model in which rats were injected with lipopolysaccharide (LPS) and then subjected to renal ischemia followed reperfusion (LPS plus ischemia-reperfusion). Ischemia-reperfusion was achieved by occluding bilateral renal artery for 60 min and then releasing for 350 min. At 50 min after ischemia started, LPS was injected intravenously. LPS plus ischemia-reperfusion induced a large amount of 3-nitrotyrosine, an oxidative product of protein that is produced via ONOO– nitration, which was not detectable in normal group. Oxidative damage of mitochondria was indicated by an accumulated thiobarbituric acid (TBA)-reactive substance, glutathione (GSH) depletion and glutathione peroxidase (GSH-Px) inactivation in the mitochondria. Treatment of rats with sanguiin H-6 (10 mg/kg body weight/day) for 30 days prior to LPS plus ischemia-reperfusion attenuated the oxidative damage in the mitochondria. The amount of TBA-reactive substance was decreased and the GSH levels significantly increased as compared with that in control group. However, its effect on GSH-Px activity was much weaker. Apoptosis induced by LPS plus ischemia-reperfusion was detected by fluorescence staining, TdT-mediated dUTP-biotin nick end labeling and electrophoretic analysis. Sanguiin H-6 appeared to inhibit apoptosis, and this was associated with the suppression of caspase-3 activity. These beneficial effects of sanguiin H-6 against oxidative damage in mitochondria and apoptosis contributed to the improvement in renal function by reversing the elevated levels of blood urea nitrogen and creatinine caused by ONOO–.

Effects of sanguiin H-6, a component of Sanguisorbae Radix, on lipopolysaccharide-stimulated nitric oxide production

The present study was conducted to evaluate the effect of sanguiin H-6, a component of Sanguisorbae Radix, on the production of nitric oxide (NO), using macrophages activated by lipopolysaccharide (LPS). Sanguiin H-6 inhibited nitrite production, taken as an index for NO, in a concentration-dependent fashion. This compound decreased inducible NO synthase (iNOS) activity, with the inhibitory effect at a concentration of 25 microM being equal to that of the known iNOS inhibitor aminoguanidine at 50 microM. However, unlike aminoguanidine, sanguiin H-6 was associated with improved cell viability. Reverse transcription-polymerase chain reaction analysis revealed that the expression of iNOS mRNA in activated macrophages was suppressed by sanguiin H-6 in a concentration-dependent manner. In addition, sanguiin H-6 even at a low concentration showed a clear scavenging effect on the NO generated from sodium nitroprusside (an NO donor). These findings indicate that not only does sanguiin H-6 act directly as an NO scavenger, but it also inhibits NO production in LPS-activated macrophages by the concomitant inhibition of iNOS mRNA induction and enzyme activity.

Inhibition of nitric oxide release by an aqueous extract of Tinospora tuberculata.

An aqueous extract of Tinospora tuberculata stems was found to scavenge nitric oxide (NO) in vitro in both cell and cell‐free systems. When the aqueous extract was added to lipopolysaccharide‐stimulated murine macrophages, it inhibited NO release dose‐dependently, and similar activity was found in a cell‐free system using sodium nitroprusside as a NO donor. These findings may help to explain, in part, certain pharmacological activities of Tinospora tuberculata. Copyright

Effect of traditional chinese prescriptions and their main crude drugs on 1,1‐diphenyl‐2‐picrylhydrazyl radical

The inhibitory effects of 79 traditional Chinese prescriptions and 28 crude drugs on the 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical were examined, and many demonstrated significant inhibition. The most effective crude drugs were Gallae Rhois and Rhei Rhizoma, followed in order by Cinnamomi Cortex, Ephedrae Herba, Scutellariae Radix, Perillae Herba, Paeoniae Ruber Radix and Moutan Cortex, while prescriptions composed of one or more of these crude drugs also showed strong free radical scavenging activity. These results predict that traditional Chinese medicines would be promising agents for scavenging free radicals, and for curing diseases related to free radical reactions.

Evidence suggesting a nitric oxide-scavenging activity for traditional crude drugs, and action mechanisms of Sanguisorbae Radix against oxidative stress and aging.

In this series of experiments, we found that Sanguisorbae Radix extract possesses strong free radical-scavenging activity in vitro and in vivo. This crude drug protected against renal disease, which is closely associated with excessive generation of reactive oxygen species. We also showed that Sanguisorbae Radix extract can suppress lipid peroxidation and stimulate an antioxidant defense ability in SAM, suggesting that this crude drug may be an effective agent for ameliorating the pathological conditions related to excessive generation of free radicals and oxidant damage, particularly in the aging process.

Protection of the kidney by Wen-Pi-Tang against ischemia-reperfusion injury.

Electrophoretic and densitometric data revealed induction of apoptosis in the kidney due to experimentally induced ischemia-reperfusion injury. Such apoptosis in the kidney was reduced in rats given 62.5 or 125 mg/kg body wt./day Wen-Pi-Tang orally for 30 days prior to ischemia-reperfusion. An increase in the dose of Wen-Pi-Tang was associated with suppressed fragmentation of DNA, a ladder pattern of low-molecular-weight molecules, resulting in a beneficial effect on renal function.