Majhi Rita, Maharjan Rukusha, Shrestha Mitesh, Mali Aatish, Basnet Angisha, Baral Manish, Duwal Rabin, Manandhar Rojlina, Rajbhandari Prajwal
Department of Natural Product and Green Chemistry, Research Institute for Bioscience and Biotechnology (RIBB), Kathmandu, Nepal.
Department of Applied Microbiology and Food Technology, Research Institute for Bioscience and Biotechnology (RIBB), Kathmandu, Nepal.
BMC Chem. 2023 Apr 13;17(1):36. doi: 10.1186/s13065-023-00948-9.
Guava (Psidium guajava Linn.) has been traditionally used in the treatment of a wide range of diseases due to its rich content of secondary metabolites.
This study was aimed to evaluate the effect of altitude and solvent systems on guava leaves crude extract's phenolics and flavonoid content, antioxidant, antimicrobial, and toxicity nature.
Guava leaves were collected from three different geographical locations in Nepal while solvents with an increasing polarity index were used for extraction. The yield percentage of extracts was calculated. Total Phenolic Content, Total Flavonoid Content, and antioxidant activity were determined by the Folin-Ciocalteu method, Aluminium chloride colorimetric method, and DPPH (2,2'-Diphenyl-1-picrylhydrazyl) assay respectively. The quantification of fisetin and quercetin was performed using the HPLC with method validation. The antimicrobial activity of the extracts was tested against bacteria and fungus isolated from spoiled fruits and vegetables and identified through 16s and 18s rRNA sequencing. Finally, Brine Shrimp Lethality Assay (BSLA) was used for testing the toxicity of the extracts.
The phenolic and total flavonoid content was found to be higher in ethanol extract (331.84 mg GAE/g dry extract) and methanol extract (95.53 mg QE/g dry extract) from Kuleshwor respectively. Water extract of guava leaves from Kuleshwor (WGK) did not show significantly different antioxidant activity when compared to methanol and ethanol extracts. Fisetin and quercetin were higher in WGK (1.176 mg/100 g) and (10.967 mg/100 g) dry extract weight respectively. Antibacterial activity against food spoilage bacteria was dose-dependent and found to be highest for all the extracts from different solvents and altitudes at higher concentrations (80 mg/ml). Similarly, methanol and ethanol guava extracts from all locations showed antifungal activity against Geotrichum candidum RIBB-SCM43 and Geotrichum candidum RIBB-SCM44. WGK was found to be non-toxic.
Our study concludes that the antioxidant and antimicrobial activity of WGK was found to be similar statistically to that of methanol and ethanol extracts of Bishnupur Katti and Mahajidiya. These results suggest the possibility of using water as a sustainable solvent to extract natural antioxidant and antimicrobial compounds which can further be used as natural preservatives to extend the shelf life of fruits and vegetables.
番石榴（Psidium guajava Linn.）由于其丰富的次生代谢产物含量，传统上被用于治疗多种疾病。
本研究旨在评估海拔高度和溶剂体系对番石榴叶粗提物中酚类和黄酮类成分、抗氧化、抗菌及毒性性质的影响。
从尼泊尔三个不同地理位置采集番石榴叶，同时使用极性指数递增的溶剂进行提取。计算提取物的得率百分比。分别采用福林 - 西奥尔特法、氯化铝比色法和DPPH（2,2'-二苯基 - 1 - 苦基肼）法测定总酚含量、总黄酮含量和抗氧化活性。使用高效液相色谱法并进行方法验证对非瑟酮和槲皮素进行定量。测试提取物对从 spoiled fruits and vegetables 中分离出的细菌和真菌的抗菌活性，并通过16s和18s rRNA测序进行鉴定。最后，使用卤虫致死试验（BSLA）测试提取物的毒性。
分别发现来自库勒什沃尔的乙醇提取物（331.84 mg GAE/g干提取物）和甲醇提取物（95.53 mg QE/g干提取物）中酚类和总黄酮含量较高。与甲醇和乙醇提取物相比，库勒什沃尔番石榴叶的水提取物（WGK）未显示出显著不同的抗氧化活性。WGK中干提取物重量的非瑟酮和槲皮素分别较高，为（1.176 mg/100 g）和（10.967 mg/100 g）。对食品腐败细菌的抗菌活性呈剂量依赖性，发现在较高浓度（80 mg/ml）下，来自不同溶剂和海拔高度的所有提取物的抗菌活性最高。同样，来自所有地点的甲醇和乙醇番石榴提取物对念珠地霉RIBB - SCM43和念珠地霉RIBB - SCM44显示出抗真菌活性。发现WGK无毒。
我们的研究得出结论，WGK的抗氧化和抗菌活性在统计学上与比什努布尔卡蒂和马哈吉迪亚的甲醇和乙醇提取物相似。这些结果表明使用水作为可持续溶剂提取天然抗氧化和抗菌化合物的可能性，这些化合物可进一步用作天然防腐剂以延长水果和蔬菜的保质期。
