Correlation analysis of flavonoid content and antioxidant activity in bamboo leaf Sichuan pepper
Bamboo leaved Sichuan pepper is the dried and mature fruit skin of the Rutaceae plant Zanthoxylum armatum DC. It is pungent and warm in nature, and has the effects of moderate temperature pain relief, insecticidal and itching relief. It is commonly known as “Tengjiao” and is also known as Wanhuazhen, Baitongguan, Zhuyetongguan, Shanjiao, etc. It is mainly distributed in the southwestern region south of Qinling Mountains in China. At present, the planting area of Sichuan Province has reached more than 3 million acres, forming three characteristic advantageous planting areas for Sichuan pepper in central Sichuan, western Sichuan, and western Sichuan. Panxi and central Sichuan are concentrated areas for bamboo leaf Sichuan pepper.
Based on its unique and fragrant flavor, bamboo leaf Sichuan pepper is widely circulated in the catering industry and is commonly used as a flavor regulator and preservative. Its preservative effect is related to antioxidant active substances. Modern pharmacological studies have shown that Sichuan pepper has analgesic, anti-inflammatory, hepatoprotective, antioxidant, mosquito repellent, insecticidal, anti-tumor, hypoglycemic, and anti Alzheimer’s disease effects. Among them, the pharmacological effects of hepatoprotective, anti-tumor, and hypoglycemic effects are related to the antioxidant activity of Sichuan pepper. Currently, there is no research indicating that the antioxidant activity of Sichuan pepper is related to its traditional efficacy. Our preliminary research has shown that different polar parts of Sichuan pepper have the ability to scavenge DPPH, ABTS, and hydroxyl radicals. There are literature reports that bamboo leaf Sichuan peppercorns from different regions have good antioxidant activity, and experiments on free radical scavenging rate, total antioxidant activity, and reduction potential all indicate a positive correlation between antioxidant activity and extract dosage. The water extract of Tengjiao has excellent antioxidant activity, which may be related to flavonoids such as rutin and quercetin. At present, there is relatively little research on the differences in flavonoid content and its correlation with antioxidant activity in bamboo leaf Sichuan pepper from different origins. Therefore, this article collected 27 batches of Sichuan Sichuan Chuanzhong, Panxi and other 21 production areas’ Sichuan  . By using Pearson correlation analysis, this study aims to explore the correlation between flavonoid components and antioxidant activity, in order to provide experimental basis for the research on antioxidant activity of bamboo leaf Sichuan pepper and the development of health derivatives.

This study used HPLC to simultaneously determine the content of rutin, hyperoside, isoquercitrin, and quercitrin in Sichuan pepper. The total flavonoid content was measured using a spectrophotometer to compare the differences in flavonoid content among different regions. The results showed that the total flavonoid content ranged from 30.4607 to 90.1731mg/g. The total flavonoid content in Tongjiang County (s12) of Bazhong City was three times that of Jiajiang County (s14) of Leshan City. The content of hyperoside ranged from 0.4427 to 3.9832mg/g. The content of hyperoside in Yanyuan County (s3) of Liangshan Prefecture was nearly 10 times higher than that in Butuo County (s8) of Liangshan Prefecture. The total flavonoid content (TL) of the four flavonoid components in Yanyuan County (s3) of Liangshan Prefecture was five times that of Butuo County (s8). There were significant differences in the content of total flavonoids and four flavonoid components in different production areas.
Using DPPH and ABTS free radical scavenging assays, the antioxidant activity of Sichuan produced bamboo leaf Sichuan pepper from 21 production areas was analyzed, and Pearson bivariate correlation analysis was used to analyze the correlation between flavonoid components and antioxidant activity. The results showed that there were significant differences in the antioxidant activity of Sichuan pepper from different regions. Bazhong Tongjiang (s12) has the highest ability to scavenge DPPH free radicals. Compared with other regions, the three batches of Bazhong bamboo leaf Sichuan pepper methanol extracts have higher ability to scavenge DPPH, which is consistent with the results of flavonoid content determination. However, Mianyang Santai has the best ability to scavenge ABTS free radicals, indicating that there are differences in the results of in vitro antioxidant activity tests.
The correlation analysis results show that there is a high consistency between the content of rutin and the total flavonoid content. Therefore, the content of rutin in Sichuan pepper can be used as an evaluation index for the level of total flavonoid content. The EC50 values of total flavonoids and rutin were significantly negatively correlated with DPPH and ABTS free radical scavenging rates, indicating that total flavonoids and rutin in Sichuan pepper have significant antioxidant effects. Zhang compared the antioxidant activities of four monomeric compounds, namely rutin, hyperoside, isoquercitrin, and kaempferol-3-O – β – D-glucopyranose, in the order of hyperoside>rutin>isoquercitrin. Currently, there is no literature reporting the antioxidant activity of quercitrin, and the content of rutin and hyperoside accounts for 57.8% to 67.3% of the total content of the four flavonoids. Therefore, rutin can be used as one of the indicators to evaluate the antioxidant activity of Sichuan pepper.
There are significant differences in the content of total flavonoids, rutin, hyperoside, isoquercitrin, and quercitrin in the determination of flavonoids in bamboo leaf Sichuan pepper from different regions. Through literature review, it was found that there are many influencing factors. Due to the concentrated origin of the samples collected in this experiment, there are certain limitations. Further research will collect samples of Sichuan peppercorns from different provinces across the country to explore the antioxidant mechanism of Sichuan peppercorns and provide empirical evidence for the development of their health derivatives.