Different leaf maturities and withering durations affect the antioxidant potential and aroma compound of Indonesian bay leaf [Syzygium polyanthum (Wight) Walp.]

Indonesian bay leaves [IBL; Syzygium polyanthum (Wight) Walp.] are frequently used as a seasoning in various Indonesian cuisines. The potential of IBL leaves extract as an antioxidant and aroma source based on the leaf maturities and withering durations is not yet known. Therefore, the present work aimed to study the effect of IBL leaf maturities and withering durations on the changes in antioxidant potentials and aroma compound. Results showed that the total phenolic, flavonoid, and tannin contents of old IBL leaves extract yielded the highest values (89.08 gallic acid equivalent (GAE)/g sample, 37.11 mg quercetin equivalent (QE)/g sample, and 2.72 mg tannic acid equivalent (TAE)/g sample, respectively) as compared to half-old and young leaves extracts. Similarly, the antioxidant activities of old IBL leaves extract were also the highest at 77.06 mg TEAC/g sample (DPPH assay), 7.92 mg TEAC/g sample (FRAP assay), and 83.19 mg TEAC/g sample (ABTS assay) as compared to half-old and young leaves extracts. The yields of essential oil and total ss-ocimene (key aroma compound) from old IBL leaves were also the highest as compared to half-old and young leaves. Nevertheless, all these parameters significantly decreased after two days of withering treatment. Therefore, in order to maximise the antioxidant capacity and aroma compound, it is henceforth suggested that IBL leaves should not be used more than two days after harvest.