Effect of total phenolic content on free radical scavenging activities of Boletes mushroom extracts

Abstract

Keywords: Boletes mushroom extract; total phenolic content; free radical scavenging activity; DPPH; ABTS

Objectives: The present study aimed to determine total phenolic content and free radical scavenging activities of Boletes mushroom extracts. The correlation between their total phenolic content and free radical scavenging activities was also determined to explain the effect of their phenolic content on antioxidant activities.

Methods: Seven mushroom extracts were prepared from fruiting body of Boletes mushrooms collected from the central and the northeastern parts of Thailand. Their phenolic content was determined by Folin-Ciocalteau method. Free radical scavenging activities of these extracts were performed on 2,2 diphenyl-1-picrythydrazyl (DPPH) and 2,2-azino-bisethylbenzthiazoline-6 sulfonic acid (ABTS) assays. The correlation between their total phenolic content and free radical scavenging activities was also investigated.

Results: Boletes mushroom extracts obtained had phenolic contents between 26.70-113.17 mg GAE/g extract. At the concentration of 100 µg/ml, these extracts exhibited 43.72-93.89% DPPH inhibition and 41.66-99.76% ABTS inhibition. TISTR Boletes 55 mushroom extract showed the highest total phenolic content and the strongest activities on both assays. IC₅₀ values of TISTR Boletes 55 were 13.63 µg/ml and 23.58 µg/ml for DPPH and ABTS scavenging activities, respectively. The correlations between total phenolic content and free radical scavenging activities of Boletes mushroom extracts showed different results. There was significant positive correlation between total phenolic content and DPPH scavenging activity but no correlation between total phenolic content and ABTS scavenging activity. Their antioxidant activities may be due to other components presented in the crude extracts.

Conclusion: Thai Boletes mushroom extracts studied showed high phenolic content and good free radical scavenging activities. Their total phenolic content significantly affected DPPH scavenging activity but did not affect ABTS scavenging activity. Other components in mushroom extracts should be further studied to evaluate their effect on antioxidant activities.