Study on the antioxidant activity and anti-aging effect of fermented kudzu root and water extracted kudzu root on nematodes
Pueraria lobata is the root of leguminous plants in the Pueraria genus, widely distributed in China. As a traditional Chinese medicinal herb, kudzu root has the effects of treating sores, relieving fever, and generating saliva. It is recorded in the “Shennong Bencao Jing”, “Bencao Shi Yi”, and “Chinese Pharmacopoeia”. With the continuous improvement of traditional Chinese medicine theory and the increasing awareness of people’s pursuit of health, many medicinal and edible plants have been developed and made into beverages and health foods. There are many plants with anti-aging effects in current research, including ginseng, kudzu root, sea buckthorn, goji berry, etc. The anti-aging active ingredients of kudzu root mainly include kudzu isoflavones, puerarin, kudzu polysaccharides, and alkaloids. Zhou et al. found that puerarin can significantly improve cognitive impairment in amyloid precursor protein/presenilin-1 mice, reduce oxidative stress levels in brain tissue, and increase the activity of antioxidant enzymes in rat blood and liver, while reducing the content of malondialdehyde. Shao et al. found that polysaccharides from Pueraria lobata have the effect of prolonging the lifespan of nematodes. Li et al.’s research has shown that compound Pueraria lobata tablets have the effects of protecting blood vessels, resisting oxidative stress damage, and slowing down vascular aging.
In order to better absorb and utilize the active ingredients of Pueraria lobata, there are various methods for extracting Pueraria lobata, such as water bath extraction, ultrasonic extraction, enzymatic extraction, etc. By utilizing fermentation technology to extract traditional Chinese medicine, the secondary metabolites produced by microbial metabolism can synergistically enhance the efficacy of the herbal ingredients. Additionally, due to the action of extracellular enzymes from microorganisms, it facilitates the release of active ingredients from traditional Chinese medicine.
Nematodes are typical model organisms for studying aging, with characteristics such as easy cultivation, short growth cycle, highly conserved evolution, and high homology with human genes. Therefore, nematodes are commonly used for screening anti-aging natural products. This article uses fermentation and water extraction methods to extract active substances from Pueraria lobata, and explores the antioxidant and anti-aging effects of Pueraria lobata fermentation broth and Pueraria lobata water extract on the antioxidant capacity, nematode lifespan, egg laying, and heat stress.

As a medicinal and edible herb, kudzu root has the effects of clearing free radicals, reducing fever and promoting diuresis, and preventing cardiovascular and cerebrovascular diseases. Among them, kudzu root flavonoids and isoflavones are its main active ingredients, which have good antioxidant properties. This article extracted the active ingredients of Pueraria lobata through fermentation and water extraction methods. It was found that the flavonoid content in the fermented extract was 4.8 ± 0.32mg/mL, significantly higher than the flavonoid content of 3.47 ± 0.23mg/mL obtained by water extraction (P<0.01). The puerarin content obtained by fermentation extraction was slightly higher and the total phenolic content was slightly lower, but there was no significant difference. To further evaluate the antioxidant and anti-aging effects of the two extracts, three in vitro free radical scavenging models were first used to test the antioxidant capacity of the extracts. The results showed that the 6.8% volume concentration of Pueraria fermentation broth had stronger total antioxidant capacity, hydroxyl radical and superoxide anion scavenging ability than the Pueraria water extract, and the Pueraria fermentation broth had better antioxidant effect.
As a model organism for aging, nematodes are widely used in the evaluation of traditional Chinese medicine extracts for delaying aging. The fermentation broth and Pueraria root extract were separately applied to Caenorhabditis elegans. Compared with the control group under normal culture conditions, the Pueraria root fermentation broth significantly prolonged the lifespan of the nematodes (P<0.05). Under heat stress conditions, the heat tolerance time of nematodes cultured in Pueraria root fermentation broth was significantly higher than that of the control group (P<0.05). The egg laying experiment showed that the fermented liquid of Pueraria lobata extended the lifespan of nematodes without sacrificing their egg laying, and its egg production was higher than that of the Pueraria lobata water extract group. The genetic testing results showed that the fermentation broth of Pueraria lobata achieved high temperature tolerance and higher antioxidant capacity by downregulating the anti-aging gene daf-2, upregulating the expression of anti-aging gene daf-16, antioxidant gene sod-3, and heat stress gene hsp-16.2, thereby prolonging the lifespan of nematodes. The mechanism of Pueraria lobata fermentation broth in prolonging nematode lifespan is shown in Figure 7.
Zhang et al. significantly increased the survival rate of nematodes fed with kudzu flavonoids compared to the control group. Shao’s research shows that the polysaccharides extracted from Pueraria lobata water can protect nematodes from heat stress damage, enhance their motility, and prolong their lifespan. Jeon’s research results indicate that puerarin has anti-inflammatory and antioxidant effects on colitis mice. It can be inferred that the effect of Pueraria lobata fermentation broth in delaying nematode aging is the result of the combined action of various substances such as flavonoids, polysaccharides, and puerarin in the fermentation broth. Based on the previous research results of our research group, the total sugar content in the water extract of Pueraria lobata (3.46 ± 0.18mg/mL) is higher than that in the fermentation broth of Pueraria lobata (2.52 ± 0.5mg/mL), but the effect of Pueraria lobata water extract on delaying nematode aging is not significant. It is inferred that flavonoids, the main functional component in the fermentation broth of Pueraria lobata, play a key role in delaying the aging of nematodes.
Our research group tested the antioxidant and anti-aging effects of Pueraria lobata water extract and Pueraria lobata fermentation broth at the biochemical and cellular levels. The results showed that Pueraria lobata fermentation broth had a good effect on scavenging DPPH free radicals at the biochemical level, and could increase the activity of antioxidant enzymes in fibroblasts and promote the expression of collagen. In order to comprehensively evaluate its antioxidant efficacy, this article supplemented the biochemical testing of the scavenging effects of two extracts of Pueraria lobata on hydroxyl radicals and superoxide anions, as well as the overall antioxidant capacity level. Due to the limitations of cell experiments, in order to further verify the anti-aging effect of kudzu root fermentation broth, this article uses the aging model organism Caenorhabditis elegans as the research object, and detects the effect and mechanism of kudzu root fermentation broth in delaying the lifespan of nematodes at the animal level. Therefore, it has more reference value. The results showed that the fermented liquid of Pueraria lobata has good antioxidant effects and can delay the aging of nematodes. It exerts anti-aging effects by regulating the expression of key genes in the insulin signaling pathway Insulin/IGF. The above results can provide some reference for the development and application of kudzu root fermentation broth in anti-aging food and cosmetics fields.