Screening of Antioxidant Capacity of Epilobium parviflorum Ecotypes Grown in Iran

Introduction: The phytochemical and biological properties of medicinal plants depend on the climatic conditions of the area under development, the growth stage, genetic factors and other factors. Therefore the study of the wild flora in the geographical areas with different climatic conditions is important. It has been proved that the extract of Epilobium has high antioxidant capacity, which is associated with a high concentration of flavonoids content. Studies on five species of Epilobium genus (E. parviflorum schreb., E. roseum schreb., E. tetragonum L., E. montanum L., E. angustifolium L.), had shown that E. parviflorum had the highest antioxidant capacity among studied species. The occurrence of E. parviflorum in wide range of altitudinal zones in Iran makes it as ideal species to study the variation of antioxidant capacity among ecotypes. The present study aims to screen Epilobium parviflorum ecotypes (n=16) of Iran in terms of antioxidant capacity (AOX). Materials and Methods: Total phenol content (TPH), Total flavonoid (TFL), antioxidant capacity (AOX) and anthocyanin content (ACY) were measured by Folin- Ciocalteu, flavonoid-aluminum chloride (AlCl3), Ferric reducing antioxidant power (FRAP) and the differential PH methods, respectively. Regression analysis was used for studying the relationships between antioxidant capacity, altitude and latitude. The Pearson correlation coefficient was used to determine whether there is a linear relationship between variables. Results and Discussion: There was a high correlation between total phenol content and total flavonoid in ecotypes (r = 0.7, P = 0.002, n = 16). There was a positive and significant correlation between AOX content with TPH (r = 0.71, P = 0.002, n = 16) and also between AOX with TFL (r = 0.73, P = 0.001, n = 16). According to several studies, high antioxidant capacity has been attributed to high concentrations of flavonoids and phenols, which is consistent with the results observed in this study. The results also showed that the Iranian E. parviflorum ecotypes had considerably TFL, TPH and AOX content as compare to previous reports on E. parviflorum (in other country) and also other Epilobium species. Principal component analysis showed that the two main components explained 87.87% total variation. The high contribution of the two first components suggested a considerable correlation between three phytochemical traits, the contribution of the first component alone was 62.13% and the portion of the second component was 25.74%. In the first component, TFL, TPH and AOX were with coefficients of 0.78, 0.77 and 0.88, respectively. The high contribution of the two first components had a significant relationship between three phytochemical traits. The ecotypes of E. parviflorum were clearly separated based on the first principal component. Ten ecotypes had a correlation with the first main component (PC1) shown by TFL, TPH and AOX. Among them six ecotypes had a positive correlation (r> 0.6) and 4 ecotypes had a negative correlation (r> 0.6) with the first main component (PC1). Thus, out of the 16 ecotypes of E. parviflorum in Iran, six ecotypes including EPP3, EPP6, EPP8, EPP10, EPP13 and EPP9 had the desired content of TFL, TPH and subsequently antioxidant capacity, most of which belonged to the Zagros and crossroad of Zagros and Alborz mountains. The ecotypes that did not have the desired content of TFL, TPH and AOX (negative correlation with the first main component, PC1) mostly belong to the Alborz Mountains. The highest levels of TPH, TFL and AOX capacity were observed for the Sangan ecotype with values of 1761, 32.64 mg/g DW and 93.50 mM/g DW, respectively, and the lowest was observed in Kaleybar ecotype. Out of 16 ecotypes, 6 ecotypes had the desired content of TFL, TPH, and subsequently AOX, most of which belonged to the Zagros and crossroad of Zagros and Alborz Mountains. Regression analysis showed no relation between AOX capacity with altitude (R2 = 0.04) and also with latitude (R2 = 0.14). Conclusion: This research is the first study that screens AOX capacity by including multiple ecotypes (n=16) from E. parviflorum species to evaluate intra ecotypes phytochemical variation for E. parviflorum. We found positive and significant correlation between TFL, TPH and AOX. We did not find any significant correlation between TFL, TPH content and AOX capacity of E. parviflorum with altitude above sea. Our results also showed Iranian E. parviflorum ecotypes (especially Sangan ecotype, EPP10) have considerably TFL, TPH and AOX capacity compared to previous reports. The results of this study indicate that there is a remarkable variation among Iranian E. parviflorum ecotypes for the studied traits, which can be used to carry out breeding programs and protection of germplasm.