Antioxidant Constituents of Almond [Prunus dulcis (Mill.) D.A. Webb] Hulls

• Published in: Journal of agricultural and food chemistry Vol. 51; no. 2; pp. 496 - 501
• Main Authors: Takeoka, Gary R, Dao, Lan T
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 15-01-2003
• Subjects: Antioxidants - analysis; Biological and medical sciences; Chlorogenic Acid - analysis; Chromatography, High Pressure Liquid; Chromatography, Thin Layer; Food industries; Fruit and vegetable industries; Fundamental and applied biological sciences. Psychology; Hydroxybenzoates - analysis; Plant Extracts - chemistry; Prunus - chemistry; Seeds - chemistry; Nuts; Prunus dulcis; Rosaceae; Chlorogenic acid; Antioxidant; Αlmond hulls; Almond; Dicotyledones; Angiospermae; Phenols; Spermatophyta; Chemical composition; HPLC; Sterol
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf020660i

Almond hulls (Nonpareil variety) were extracted with methanol and analyzed by reversed phase HPLC with diode array detection. The extract contained 5-O-caffeoylquinic acid (chlorogenic acid), 4-O-caffeoylquinic acid (cryptochlorogenic acid), and 3-O-caffeoylquinic acid (neochlorogenic acid) in the ratio 79.5:14.8:5.7. The chlorogenic acid concentration of almond hulls was 42.52 ± 4.50 mg/100 g of fresh weight (n = 4; moisture content = 11.39%). Extracts were tested for their ability to inhibit the oxidation of methyl linoleate at 40 °C. At an equivalent concentration (10 μg/1 g of methyl linoleate) almond hull extracts had higher antioxidant activity than α-tocopherol. At higher concentrations (50 μg/1 g of methyl linoleate) almond hull extracts showed increased antioxidant activity that was similar to chlorogenic acid and morin [2-(2,4-dihydroxyphenyl)-3,5,7-trihydroxy-4H-1-benzopyran-4-one] standards (at the same concentrations). These data indicate that almond hulls are a potential source of these dietary antioxidants. The sterols (3β,22E)-stigmasta-5,22-dien-3-ol (stigmasterol) and (3β)-stigmast-5-en-3-ol (β-sitosterol) (18.9 mg and 16.0 mg/100 g of almond hull, respectively) were identified by GC-MS of the silylated almond hull extract. Keywords: Almond hulls; antioxidant; HPLC