Comparison of total polyphenol content, antioxidant activity, and antimicrobial potential among nine cactus pear (Opuntia spp.) cultivars and their by-products

Authors

  • Jorge Dávila-Aviña
  • Bernardo Gallegos-Ruiz
  • Santos García
  • Norma Heredia

Keywords:

Opuntia spp., tender cladodes, antioxidant capacity, antimicrobial potential.

Abstract

Nopal cacti (Opuntia spp.) are important natural resources in semi-arid zones throughout the
world, where their fruits and stems are used as forage or human food depending on the variety
and ripeness of the cladode. Members of the genus Opuntia show variable phytochemical
composition as well as a high capacity for adaptation to extreme environmental conditions. One
part of the process to prepare and use of “nopalitos” for human consumption includes removal
of modified leaves or thorns, which is approximately 20% of the fresh weight of cladodes is
considered as a by-product (production residue). The objective of this study was to evaluate
the phytochemical composition, antioxidant capacity, and antibacterial potential of cladodes
and cladode by-products from nine nopal cultivars. Young cladodes (<1 month, nopalitos) and
their corresponding by-products were washed, dried, and macerated in ethanol. Ethanol
extracts were isolated by evaporation and resuspended in water. Total phenols and flavonoids
were quantified, and antioxidant capacity was assessed by spectroscopic assays [trolox
equivalent antioxidant capacity (TEAC) and percent inhibition of diphenylpicrylhydrazyl (DPPH)
radicals]. Antimicrobial activities of the extracts against Vibrio cholerae and Clostridium
perfringens were determined by the well diffusion method and calculation of minimal
bactericidal concentration (MBC) by agar plate assay. All extracts tested showed antioxidant
and antibacterial activities. Extracts of cladodes and their corresponding by-products showed
similar MBCs for C. perfringens (around 15 mg ml-1) and V. cholerae (4.0 mg ml-1). However,
extracts of cladode by-products showed higher antioxidant capacity than those of cladodes
according to both DPPH and TEAC assays. Higher concentrations of phenols and flavonoids
were also found in the extracts of by-products (ranging from 91.23 to 853.78 mg gallic acid
equivalents per gram dry weight and from 17.10 to 39.42 mg quercetin equivalents per gram
dry weight, respectively). This study demonstrates that nopal cactus species exhibit higher
antioxidant activity and contents of both phenols and flavonoids in cladode by-products than
that in their corresponding cladodes. Our data indicate that discarded cladode by-products may
be are a potentially valuable resource for nutraceutical and drug development.

Published

2018-09-14

Issue

Section

Scientific Papers