Antibacterial Activity of Kaempferia parviflora and Curcuma longa at Different Harvest Periods on Pathogenic Bacterial Isolates of Fish and Shrimp

Abstract

Due to food safety and public health concerns, much interest has been placed on
antibacterials derived from natural products for use in aquaculture. Kaempferia parviflora and
Curcuma longa, herbs that can be found in Thailand, have been shown to possess antibacterial
properties. The biological activities of these herbs, however, was found to be dependent on age.
Here, ethanol extracts of K. parviflora and C. longa harvested at different periods were evaluated for
their antibacterial activity against 5 strains of bacteria, pathogenic to aquatic animals, using disc
diffusion method. Our results revealed that K. parviflora ethanol extracts at 9 and 10 months after
planting showed antibacterial activity only against Vibrio harveyi and V. parahaemolyticus, while C.
longa ethanol extracts at 7, 8, 9 and 10 months after planting exhibited antibacterial activity against
V. harveyi, V. parahaemolyticus, Edwardsiella tarda and Streptococcus agalactiae. Both K.
parviflora and C. longa ethanol extracts show no inhibitory effect on Escherichia coli. Comparison
of the zone of inhibitions suggest that the suitable time to harvest K. parviflora and C. longa for
ethanol extraction was 9 and 10 months after planting, respectively. The minimum inhibitory
concentrations of K. parviflora and C. longa ethanol extracts during the above mentioned periods
ranged from 12.50 to 50.00 and 3.12 to 50.00 mg/ml, respectively. In conclusion, both herbs have
exhibited antibacterial activity against V. harveyi, V. parahaemolyticus, E. tarda and S. agalactiae.
C. longa ethanol extract, specifically, showed better inhibitory properties and can thus be potentially
useful for aquaculture in the treatment of bacterial infections