Halogenated Analogs to Natural A-Type Proanthocyanidins: Evaluation of Their Antioxidant and Antimicrobial Properties and Possible Application in Food Industries.

A description of new antimicrobial agents suitable for food industries has become necessary, and natural compounds are being considered as promising sources of new active derivatives to be used with the aim of improving food safety. We have previously described desirable antimicrobial and antibiofilm activities against foodborne bacteria by analogs to A-type proanthocyanidins (PACs) with a nitro (NO ₂ ) group at carbon 6 of the A-ring. We report herein the synthesis of eight additional analogs with chloro and bromo atoms at the A-ring and the systematic study of their antimicrobial and antioxidant activities in order to evaluate their possible application as biocides or food preservatives, as well as to elucidate new structure-activity relationships. The results from this study show that halogenated analogs to natural A-type proanthocyanidins rise above the nitro derivatives previously reported in their antimicrobial activities. Gram-positive bacteria are the most sensitive to all the analogs and combinations assayed, showing MICs from 10 to 50 μg/mL in most cases, as well as reductions in biofilm formation and the disruption of preformed biofilms of at least 75%. Some structure-activity relationships previously described have also been corroborated. Analogs with just one OH group at the B-ring show better antimicrobial activities than those with two OH groups, and those analogs with two or three OH groups in the whole structure are more active than those with four OH groups. In addition, the analogs with two OH groups at the B-ring and chloro at the A-ring are the most effective when antibiofilm activities are studied, especially at low concentrations.