Abstract
A randomized complete randomized design (RCBD) 3 by 3 experiment was designed to investigate and distinguish the relationships among production of secondary metabolites (total phenolics, TP; total flavonoids, TF), gluthatione (GSH), oxidized gluthatione (GSSG), soluble carbohydrate and antioxidant activities of the Malaysian medicinal herb Labisia pumila Blume under three levels of CO2 enrichment (400, 800 and 1,200 µmol mol−1) for 15 weeks. It was found that the treatment effects were solely contributed by interaction of CO2 levels and secondary metabolites distribution in plant parts, GSH, GSHH and antioxidant activities (peroxyl radicals (ROO), superoxide radicals (O2), hydrogen peroxide (H2O2) and hydroxyl radicals (OH). The records of secondary metabolites, glutahione, oxidized gluthathione and antioxidant activities in a descending manner came from the leaf enriched with 1,200 µmol/mol CO2 > leaf 800 µmol/mol CO2 > leaf 400 µmol/mol CO2 > stem 1,200 µmol/mol CO2 > stem 800 µmol/mol CO2 > stem 400 µmol/mol CO2 > root 1,200 µmol/mol CO2 > root 800 µmol/mol CO2 > root 400 µmol/mol CO2. Correlation analyses revealed strong significant positive coefficients of antioxidant activities with total phenolics, flavonoids, GSH and GSHH indicating that an increase in antioxidative activity of L. pumila under elevated CO2 might be up-regulated by the increase in production of total phenolics, total flavonoids, GSH, GSHH and soluble sugar. This study implied that the medicinal potential of herbal plant such as L. pumila can be enhanced under elevated CO2, which had simultaneously improved the antioxidative activity that indicated by the high oxygen radical absorbance activity against ROO, O2, H2O2, and OH radicals.
Highlights
Carbon dioxide is one of the most limiting factors in photosynthesis
Correlation analyses revealed strong significant positive coefficients of antioxidant activities with total phenolics, flavonoids, GSH and GSHH indicating that an increase in antioxidative activity of L. pumila under elevated CO2 might be up-regulated by the increase in production of total phenolics, total flavonoids, GSH, GSHH and soluble sugar
The present results are in agreement with those from Norhaiza et al [30] and Karimi et al [34] where they found the highest bioactive compound of L. pumila was highest accumulated in the leaf than other plant parts
Summary
Carbon dioxide is one of the most limiting factors in photosynthesis. The possibility of improving photosynthesis in crops through CO2 enrichment has interested agriculturists for many years [1]. It is interesting to note, that several studies that have looked at the effects of atmospheric CO2 enrichment on plant antioxidative compounds have found increased concentrations of these plant constituents as well as increase in activity against peroxyl radicals (ROO), superoxide radicals (O2), hydrogen peroxide (H2O2) and hydroxyl radicals (OH) [25]. Results of elevated CO2 exposure on total phenolics and flavonoids have been reported by Ibrahim et al [33], there is no available information on the effect of CO2 concentration on the production of secondary metabolites and scavenging capacity against active oxygen species for this plant species. This study was performed to evaluate the effects of elevated carbon dioxide enrichment on the concentration of phenolics, flavonoids, glutathione (GSH), gluthatione oxidase (GSSG) and antioxidative activity in the ethanolic extracts of L. pumila. The relationships among parameters of total phenolics, flavonoids, gluthatione, glutatione oxidase and antioxidative activity [peroxyl radicals (ROO), superoxide radicals (O2), hydrogen peroxide (H2O2) and hydroxyl radicals (OH·)] were established
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