Objective The objective of this study was to evaluate the total flavonoid content (TFC), total phenolic content (TPC), and antioxidant activity of hydrosols derived from six aromatic plant species cultivated in Guangxi, China ( Eucalyptus grandis × E. urophylla , Pogostemon cablin (Blanco) Benth., Cymbopogon citratus (DC.) Stapf, Rosmarinus officinalis L., Plumeria rubra L., and Baeckea frutescens L.). Furthermore, the correlations among these parameters were analyzed. Methods The volatile components of the hydrosols were analyzed by gas chromatography - mass spectrometry (GC - MS). The total flavonoid content of the hydrosols was determined by the sodium nitrite - aluminum nitrate colorimetric method. The total phenolic content of the hydrosols was measured by the Folin - Ciocalteu colorimetric method. The antioxidant activity of the hydrosols was assessed by the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging method and the 2,2′-Azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS + ) radical scavenging method. Results According to the GC - MS analysis results, among the three hydrosols in which phenolic compounds were detected, the Plumeria rubra hydrosol had the highest phenolic compound content. In the results of total flavonoid and total phenolic content measurements, the Plumeria rubra hydrosol had the highest total flavonoid and total phenolic contents, which were 74.88 ± 3.28 μg/ml and 117.80 ± 2.03 μg/ml, respectively. In the antioxidant activity measurement results, Plumeria rubra hydrosol showed the highest DPPH and ABTS + radical scavenging activities, with IC 50 values of 8.45 mg/mL and 53.65 mg/mL, respectively. Conclusion The relationship plots between the total flavonoid and total phenolic contents of the hydrosols and the IC 50 values of the hydrosols for DPPH and ABTS + radical scavenging capacity show that there are negative correlations between them. This study demonstrates a significant correlation between the total flavonoid, total phenolic content and antioxidant activity in six aromatic plant hydrosols.
Li et al. (Wed,) studied this question.