Polyphenolic compounds are known to be one of the most valuable secondary metabolites
produced in plants [1]. They have several medicinal and pharmacological importance
[2]. They are known to play a physiological resistance mechanism in plants to help
them face different types of stresses [3]. The present study aims to investigate the
effect of different molar concentrations of the plant growth regulator; salicylic
acid (SA), on some secondary metabolites of Thymus vulgaris L. exposed to decreasing
amounts of irrigating water. The accumulation of flavonoids and polyphenols in the
alcoholic extracts in different plant treatments was measured. The total flavonoid
content in control plants was 6.135 ± 0.327 rutin equivalent/g dry weight and increased
in drought plants (receiving 25% field capacity) sprayed with 3mM SA to reach 32.055
± 0.095 mg rutin equivalent/g dry weight. Also, total phenolic content increased from
8.476 ± 0.344 to 68.510 ± 1.241 mg gallic acid equivalent/g dry weight in the same
plant treatment. Radical scavenging activity on DPPH free radical was measured for
the different plant treatments. IC50 for control plants was 74.36 ± 0.39 µg/ml and
decreased to reach 36.55 ± 0.86 µg/ml in drought plants sprayed with 3mM SA. Comparison
between the polyphenolic content in control plants and plants with highest total polyphenol
content was carried out using LC/MS. Several flavonoids and polyphenolic compounds
were identified.
[1] Lin D, Xiao M, Zhao J, Li Z, Xing B, Li X, Kong M, Li L, Zhang Q, Liu Y, Chen
H, Qin W, Wu H, Chen S. Molecules 2016; 21: 1374.
[2] Alu'datt M, Rababah T, Alhamad M, Al-Mahasneh M, Almajwal A, Gammoh S, Ereifej
K, Johargy A, Alli I. Food Chem 2017; 218: 99 – 106.
[3] Mazid M, Khan T, Mohammad F. Biology and Medicine 2011; 3: 232 – 249.
