Abstract Antioxidant activities, total phenolic content (TPC), and total catechin content were analyzed in the ethanol extracts of 10 sugar apple (Annona squamosa L.) cultivar peels grown in Thailand. Antioxidant activity assays carried out in the this study were the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, ferric ion reducing antioxidant power (FRAP), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation scavenging activity, and oxygen radical absorbance activity (ORAC). ‘Nhur Thong’, ‘Nung Keaw’, and ‘Fai Keaw’ showed high percentage fruit peel (over 38.0%). ‘Nhur Thong’, ‘Nung Keaw’, and ‘Fai Keaw’ ethanol extracts possessed high antioxidant capacities in the majority of methods used, and thus could be potential candidate of natural antioxidants. ‘Fai Keaw’ showed the best activity in the ABTS (1.57 mmol of trolox/g dry sample), FRAP (0.43 mmol of trolox/g dry sample), and ORAC assays (2.84 mmol of trolox/g dry sample), as well as the highest content of TPC (140.4 mg) per gram dry sugar apple peel among the 10 cultivars. TPC showed a positive correlation compared with all antioxidant activity assays. In conclusion, ‘Fai Keaw’ could be utilized as an excellent phenolic compound source for functional food products.

Antioxidant activities and total phenolic content (TPC) were analyzed in ethanol extracts of 11 marigold cultivars grown in Thailand. Antioxidant activity assays performed in this study were the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity, ferric ion reducing antioxidant power (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, oxygen radical absorbance activity (ORAC), and superoxide anion radical scavenging activity (SRSA) assays. ‘Optiva Orange’ showed the best activity in the ORAC assay and in % SRSA, as well as the highest content of lutein (20.59 mg), gallic acid (25.77 mg), and quercetin (12.61 mg) per gram dry marigold petal among the 11 cultivars. Furthermore, ‘Optiva Orange’ showed the highest lutein yield per plant, as compared to other cultivars. In contrast, ‘Rodeo Gold’ showed the highest activity by ABTS testing (0.92 mmol of trolox/g dry sample), as well as an 89.90% inhibition of DPPH. Lutein content showed a positive correlation with TPC and all antioxidant activity assays. In conclusion, ‘Optiva Orange’ and ‘Rodeo Gold’ could be utilized as a good lutein source for functional food products and cosmetics.