English abstract
Phytonutrients (phenolic compounds and flavonoids) are secondary plant metabolites and play a significant role in defense system against pathogens as well as protection from oxidative injury due to their potential ability to neutralize reactive oxygen species including peroxides. Total phenolic content (TPC), total flavonoid content (TFC), the total antioxidant capacity (TAC), scavenging activity against H2O2 as well as brine shrimp (Artemia salina) lethality of aqueous extracts of commonly used native plants from wild and Oman Botanic Garden (OBG) were evaluated. The studied plants were reported to have wide ranges in the investigated parameters. The TPC ranged from 0.52 to 65.14 mg GAE/ g dry solid while TFC ranged from 0.07 mg to 37.14 mg CE/ g dry solid. In addition, TAC ranged from 168.27 to 1046.84 umol TE/ g and the percentages of scavenging activity spanned from 6.9 to 91.9 %. Among a total of 30 plant species examined, Pteropyrum scoparium (PS), Moringa peregrina (MP), Dodonaea viscosa (DV), Rhus aucheri (RA), Acridocarpus orientalis (AO) and Prosopis cineraria (PC) showed high values in almost all parameters. Significant positive correlation coefficients obtained between TPC and TFC and TAC and scavenging activity suggest contribution of phenolics and flavonoids to the overall antioxidant properties of the aqueous extracts. The plants from the wild and OBG exhibited variability in TPO and TFC. Several factors (e.g. abiotic and developmental stages of some sampled plants) were suggested and discussed for influencing their secondary metabolites production, but the study was not conclusive on a specific factor. Nevertheless, there was no significant difference in TAC between plants species from the wild and OBG. At the exposure levels of Ito 1000 ug/ml, the lethality brine shrimp test of four plants (M. peregrina, P. scoparium, R. aucheri and P. cineraria) having the highest values in TPC, TAC and scavenging activity revealed that they may be safe for consumption as food or medicine. In general, the results of our study revealed that some Omani plant species might be considered as potential sources for production of phenolic compounds and flavonoids. These plants can be propagated and their secondary metabolites may be utilized in food and nutraceutical industry, It is also recommended to include these plants species in the food chain of the Omani population as a dietary intervention to combat oxidative stress-mediated human chronic diseases.
