| Polydatin derivatives and analogues are pharmacologically active substances, with anti-inflammatory, antioxidant and radiation-resistant activities. However, the amounts directly extracted from plants are less while chemical synthesis will result in environmental pollution and drug residues. Therefore, it is necessary to explore a new and environment friendly synthetic pathway. Strawberry, the nutrition rich food, has edible and medicinal values. However, strawberry is easy to rotten due to the thin skin and high water content and it will result in huge economic losses. Currently, the commonly used chemical preservatives are environmentally polluted and do harm to human health while others preservation technologies require expensive equipments and complicated operation process. Therefore, it needs to find new economic, simple and easily accepted methods for strawberry preservation. In conclusion, this test to study if the endophytes isolated from Polygonum cuspidatum was able to transform polydatin to polydatin derivatives or analogues, with bioactivity, to lay the ground for a comprehensive understanding of the biological activity of polydatin derivatives or analogues and research and development of new drug. Study the antioxidant and antibacterial activity of endophytic fermented liquid, to provide theoretical basis for its research utilization. Study the strawberry postharvest storage test use fermented liquid, with the selected fruit is "brandy" strawberry, and discuss the effect and mechanism of fresh-keeping, to provides the new direction of fresh-keeping agent for strawberry preservation, and eventually lay the ground for the development and application of the endophyte. The results are as follows:1. Endophytes screening test for the microbial transformation of polydatin was implemented using thin layer chromatography (TLC). The results show that endophytic strain J3 could transform polydatin to form transformed derivatives. The endophytic strain was identified via morphological characteristics and the analysis of ITS-5.8S rDNA region. The results show that it was identified preliminarily as Aspergillus fumigatus with Genbank accession number of KM 434883.2. Transformed derivatives of polydatin were isolated and purified by macroporous adsorption resin, preparative TLC and high performance liquid chromatography. Using vitamin C (VC), BHT, polydatin and 5 kinds of polydatin derivatives as the reference substances, the DPPH-and-OH radical scavenging capacities of transformed derivatives were investigated. The results show that the transformed derivatives A-2 shows DPPH-radicals and OH-radical scavenging capabilities in vitro, and the OH-radicals scavenge ability (IC50 0.28±0.03 mg/mL) is higher than the substrate polydatin (0.75±0.13 mg/mL). However, the A-1 doesn’t show scavenging DPPH-radicals and OH-radicals capabilities in vitro.3. Detect the inhibition activities of nine kinds of pathogenic fungi of J3 fermented liquid by agar diffusion plate method. The results show that strongest inhibition of 1 g/mL fermented liquid is to Sclerotinia sclerotiorum and Colletotrichum capsici (syd.) Bull. (Inhibitory rate were 31.50%±0.02 and 31.00%±0.01, respectively).Fermented liquid have obvious inhibitory effect to Phytophthora infestans(Mont.)de Bary, Sclerotinia sclerotiorum and Alternaria brassicae compared with unfermented liquid, the inhibitory rate were 17.50%±0.02, 31.50%±0.02 and 22.50%±0.02, respectively. Detection the inhibition activities to five kinds of spoilage bacteria of J3 fermented liquid by round filter paper method and double dilution method. The highly sensitive inhibition of 1 g/mL fermented liquid is to Salmonella (Inhibitory zone diameter was 15.56±0.16 mm), MIC and MBC was 62.5 mg/mL and 125.0 mg/mL, respectively. Compared with unfermented liquid, the fermented liquid has significantly enhanced inhibition to Staphylococcus aureus, Escherichia coli, Bacillus subtilis and Salmonella. And Fermented liquid (Inhibitory zone diameter was 12.59±0.07 mm) is highly sensitive to Staphylococcus aureus compared with unfermented liquid (Inhibitory zone diameter was 6.80±0.05 mm). For Escherichia coli, Bacillus subtilis and Salmonella from low sensitive to moderate sensitivity.4. Detect the antioxidant activities of J3 fermented liquid by scavenging DPPH·、·OH and O2-· free radical method in vitro. The results show it has capabilities to scavenge the three radical in vitro, and the ability to scavenge DPPH·and·OH radical of fermented liquid (IC50 was 7.81×102±29.03 μg/mL and 6.17×104+615.31 μg/mL, respectively) is significantly higher than unfermented liquid (IC50 was 9.83×102±8.09 μg/mL and 1.07×105±407.28 μg/mL, respectively).5. At room temperature (10～13℃),1 g/mL J3 fermented liquid was used to strawberry preservation test (8 days storage). By recording strawberry decay rate, weightlessness rate, detecting content of soluble protein, soluble sugar, titratable acid, VC, MDA and enzyme activity of SOD, POD, soften cellulose during storage. Meanwhile, comparing and researching with 80 μg/mL resveratrol,80 μg/mL polydatin. Results show that at the end of the storage, compared with the blank control group, J3 fermented liquid group significantly reduce the rot rate (40.81%) and weightlessness rate (10.15%) of strawberry, and maintaining high protein(Descent rate is 69.57%), soluble sugar(Descent rate is 8.78%), titratable acid(Descent rate is 22.22%) and VC (Descent rate is 43.08%)content. And it has preferable protection of enzyme activities of SOD (4.38 U/g-min) and POD (17 U/g-min), lower softening cellulase enzyme activity (Increased to 2.18 twice) and inhibit the increase of MDA (Increased to 3.75 twice), would prolong strawberry storage period 2 days. Compared with other treatment group, fermented liquid group of strawberry significantly reduce the rot rate and the weightlessness rate during storage, reducing the consumption of nutrients, better keep fruit quality; Compared with resveratrol group, can prolong strawberry storage period 1 day. Fermented liquid processing strawberry preservation effect is best. |
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