Lethal efficacy of extract fromZingiber officinale (traditional Chinese medicine) or [6]-shogaol and [6]-gingerol inAnisakis larvae in vitro

Abstract

The authors previously reported that an extract fromZingiber officinale, traditionally eaten along with raw fish and used in traditional Chinese medicine, effectively destroyedAnisakis larvae in vitro. In this study, we analyzed the effective components of ginger rhizomes. Methanol extracts were fractionated after first being treated with HCl at pH 3, then with NaHCO₃ at pH 10, and, finally, with NaOH at pH 13 (fraction 1). In general, this fraction is rich in neutral substances. [6]-Shogaol and [6]-gingerol, known neutral components of ginger rhizomes, were detected using gas chromatography and were found to be the most prevalent components in the fraction, occurring in quantities that resulted in a dose-dependent killing efficacy. Authentic [6]-shogaol and [6]-gingerol could killAnisakis larvae at a minimal effective dose of 62.5 and 250 μg/ml, respectively. However, the concentration of [6]-gingerol in fraction 1 was >20 times that of [6]-shogaol, making the former the most active component in the fraction. Furthermore, synergistic effects between [6]-gingerol and a small amount of [6]-shogaol were observed. Pyrantel pamoate, an available antinematodal drug, had no lethal effect, even at a concentration of 1 mg/ml. In saline solution containing [6]-shogaol (62.5 μg/ml), >90% of larvae lost spontaneous movement within 4 h and were destroyed completely within 16 h. Microscopical examinations showed destruction of the digestive tract and disturbances of cuticulae.