The phenolic acids in free phenolic
acid (FPHA), methanol-soluble phenolic ester (MSPE), and methanol-soluble phenolic glycoside (MSPG) fractions of
two carob products, natural carob-pod flour (CPF) and commercial carob-pod
flour (CCPF), were identified and quantified using high-performance liquid
chromatography-mass
spectrometry (HPLC-MS). Six phenolic acids were identified in the carob flours
(gallic acid, protocatechuic acid, gentisic acid, syringic acid, p- coumaric acid, and sinapic acid).
Gallic acid was the major phenolic acid; and its concentrations in CCPF were
substantially higher than
in CPF (135 - 166
and 85.2 - 91.3 mg/g dw, respectively). The concentrations of p-coumaric acid and sinapic acid were
also higher in CCPF than in CPF. In contrast, the concentrations of
protocatechuic acid and gentisic acid were generally lower in CCPF than in CPF,
with the only exception being gentisic acid glycosides. Both carob-pod flours
contained almost the same amount of sinapic acid and syringic acid. The total
phenolic contents of the FPHA, MSPE, and MSPG fractions of CPF were found to be
44%, 38%, and 69% that of the respective fractions of CCPF. Correspondingly,
the FPHA, MSPE, and MSPG fractions of CCPF had higher free radical-scavenging activity (28.4%, 33.1%, and
26.2%, respectively) than the corresponding fractions of CPF (9.2%, 28.0%, and
9.2%, respectively). Notably, the FPHA and MSPG fractions of each sample had very similar
scavenging activity while the MSPE fraction always had higher activity. The FPHA and
MSPG fractions of CPF had the lowest activities.