2.9.1. Total soluble phenolic compounds

Total soluble phenolics (TSP) were assessed using the Folin-Ciocalteu reagent as previously described by Kähkönen et al. (Kähkönen et al., 1999) with minor modifications as in our previous study (El-Nagar et al., 2022, 2023). Briefly, about 100 mg of homogenized fresh tissues were extracted with 20 mL of 80% methanol for 24 h in the dark, centrifuged and the supernatants were collected. Subsequently, 200 μl of the supernatant was mixed with one ml of Folin-Ciocalteu reagent (10%), vortexed for 30 seconds, and set on the bench for three min, then 800 μl of 7.5% sodium carbonate was added to the mixture. Subsequently, the mixture was incubated at room temperature for 30 min, and the absorption was measured at 765 nm (A₇₆₅) using a UV-160A spectrophotometer (Shimadzu, Japan). The TSP content is expressed as mg of gallic acid equivalents per gram of fresh weight (mg GAE g⁻¹ FW).