Evaluation of the antibacterial activity of leaf and twig extracts of stout camphor tree, Cinnamomum kanehirae, and the effects on immunity and disease resistance of white shrimp, Litopenaeus vannamei

Effects of essential oils and hot-water extracts isolated from leaf and twig of stout camphor tree,
Cinnamomum kanehirae on antibacterial activity to pathogen of fish, abalone, marine fish and freshwater
prawn, and the white shrimp, Litopenaeus vannamei immunity and disease resistance to Vibrio alginolyticus
were carried out in this study. A better antibacterial activity against nine selected pathogen
bacteria was recorded in twig essential oil, and the selected pathogens of both Gram-positive bacteria
and Gram-negative bacteria were sensitive to the leaf and twig essential oils in the present study. No
antibacterial activity was recorded in the hot-water extracts of leaf and twig. In challenge trial,
a significant decrease of sensitivity to V. alginolyticus (1 106 cfu shrimp1) was found in that of shrimp
received hot-water extract from twig at the levels of 2 mg g shrimp1 compared to control. In addition,
the how-water extract of twig in vitro showed greater enhanced effects on phenoloxidase activity,
respiratory burst and phagocytosis of white shrimp compared to the hot-water extract of leaf. It is
considered that the extracts of stout camphor tree could be a candidate to replace the chemo-therapeutants
through the inhibitory effects against the growth of pathogens, and enhanced effects on
shrimp immunity and disease resistance.