The Antioxidant And Antitumor Components From Lithospermum Erythrorhizon

Some familiar traditional Chinese medicines were selected and their antioxidant effects were evaluated using the Oxidative Stability Instrument (OSI) method. Among them, Lithospermum erythrorhizon and Polygonum cuspidatum were found to have significant antioxidant effects on retarding the peroxidation of lard. The antioxidant activity of the former one was even stronger than the synthetic antioxidant BHT and the natural antioxidantα-tocopherol. Few reports, however, have addressed the antioxidant activity of L. erythrorhizon. So it may be worth of studying as a potential antioxidant resource and a series of research on its antioxidant activity had been performed in this paper.The antioxidant effects of crude powder and different polarity extracts of L. erythrorhizon at different concentrations were tested in lard. As a result, the 0.02%-1.5% of the powder obviously prolonged the induction period of lard oxidation from 4.5 h to 6.0 h-87.4 h respectively in a good dose-dependent manner. The petroleum ether extract and chloroform extract of L. erythrorhizon were also exerted strong antioxidant activity. These results suggested that L. erythrorhizon could be considered as a promising source of natural antioxidants.On the basis of antioxidant-guiding, various chromatographic techniques were performed to isolate active constituents from the above two main fractions of L. erythrorhizon. Seven compounds were isolated and identified by UV, IR, NMR and MS spectra data and physical-chemical properties. They were identified as deoxyshikonin (1),β,β-dimethylacrylshikonin (2), isobutylshikonin (3), shikonin (4), 5,8-dihydroxy-2-(1-methoxy-4-methyl-3-pentenyl)-1,4-naphthalenedione (5),β-sitosterol (6) and a mixture of two caffeic acid esters (7). Among them, compound 5 was isolated from this plant species for the first time. The antioxidant activities of the seven compounds were compared and evaluated through Rancimat method, reducing power and radical scavenging activity. Their action mechanisms were also preliminarily explored. Results showed that, except compound 6, other six compounds all exhibited obvious antioxidant activities against four different methods. Compounds 4 and 7 exerted much more potent antioxidant effects on retarding the lard oxidation than that of BHT and both were found to exhibit strong reducing power. Their antioxidant activities, assessed by Rancimat method and reducing power, decreased in the following order respectively: compound 7 > 4 > BHT> 2 > 3 > 5 >1 >6 and compound 7 > BHT > 4 > 2～3～5 > 1 >6. In addition, compounds 1-5 all exerted very good radical scavenging activities toward ABTS⁺ but showed moderate scavenging activities toward DPPH, while compound 7 presented as a powerful radical scavenger against both ABTS⁺ and DPPH. Thus, this study furnishes additional dada to the literature about compounds with antioxidant activity from L. erythrorhizon.In the experimental research, the antioxidant activities and anti-fatigue effects of L. erythrorhizon were performed in vivo for the first time andα-tocopherol was used for the comparison purpose. After mice were orally treated with extracts of L. erythrorhizon for 3 weeks, the serum level of SOD was significantly increased (P<0.05 or P<0.01) and the level of MDA was significantly decreased compared to the control group (P<0.05 or P<0.01). Further, they also could lessen fatigue by prolonging the swimming time of the burdened mice. These evidenced that L. erythrorhizon could exhibit bioactivity in vivo.The study examined the in vitro antitumor activities of the 7 compounds isolated from L. erythrorhizon. MTT assays were used to explore their inhibiting effect on the proliferation of MGC-803 and BEL-7402 human cancer cell lines. Diamminedichloroplatinum (DDP) was used as comparison sample and the cytotoxicity effect was evaluated using growth inhibition ratio and IC₅₀ value. The results showed that seven compounds exhibited different antitumor effects. The IC₅₀ values of compounds 1-7 and DDP toward MGC-803 cell were 1.7,1.4,7.0,0.5,1.5,> 100,> 100 and 4.4μg/mL, respectively; and toward BEL-7402 cell were 1.5,1.3,34.0,1.3,1.4,> 100,>100 and 7.6μg/mL, respectively. It can be concluded that naphthoquinone compounds (1-5) from L. erythrorhizon possessed strong antitumor activities against MGC-803 and BEL-7402 in vitro and in a concentration dependent manner. In addition, among the isolated compounds, compounds 1, 2, 4 and 5 exhibited stronger antitumor activity than DDP while compounds 6 and 7 had no antitumor effect in this study.RP-HPLC method for the simultaneous determination of shikonin, isobutylshikonin andβ,β-dimethylaerylshikonin in L. erythrorhizon was developed and validated. The linear ranges for shikonin, isobutylshikonin andβ,β-dimethylacrylshikonin were 1.22-12.2μg.mL^-1 (r=0.9999), 2.48-24.8μg-mL-1 (r=0.9998) and 11.28- 112.8μg-mL^-1 (r=0.9998), respectively. The average recoveries were 100.3% with RSD 3.2%, 98.6% with RSD 3.0%, and 98.4% with RSD 3.3%, respectively. The methods were simple and accurate and could be used as the quality control methods of L. erythrorhizon.Under the direction of pathobiology theory of free radicals, this paper studied the antioxidant activity of L. erythrorhizon systematically, which may help the development and utilization of more effective and newly antioxidants from natural origins and endow the deep going research on L. erythrorhizon a great practical significance.