Study on Combretum indicum extracts against Giardia intestinalis in vitro

In order to observe the effects of traditional Chinese medicine Combretum indicum extracts against Giardia intestinalis（referred to as Giardia） in vitro, in this experiment, ethanol and deionized water were used to extract Combretum indicum to obtain Combretum indicum alcohol extracts and Combretum indicum water extracts.Combretum indicum alcohol extracts group, Combretum indicum water extracts group, and metronidazole control group（the concentrations were 0.312 5, 0.625, 1.25, 2.5, 5 mg/mL）, and blank control group（TYI-S-33 medium）, were set respectively.Giardia was cultured anaerobically at 37 ℃ at a concentration of 8.0×10~5-4.2×10~6 trophozoites/mL for 24 h, respectively. Adherent Giardia were collected and half of the inhibitory concentration(IC₅₀) was calculated. The Giardia were exposed to Combretum indicum water extracts, Combretum indicum alcohol extracts, and metronidazole using IC₅₀, respectively; and at the same time a blank control was set to culture for 0, 2, 4, 6, 8, 12, 24 h. The shortest action time of the drugs up to IC₅₀ was calculated. The IC₅₀ group of Combretum indicum alcohol extracts and blank control group with action time of 6 h and 12 h respectively were observed under inverted light microscopy, scanning electron microscopy and transmission electron microscopy to analyze the effects of Combretum indicum alcohol extracts on the ultramorphological structure of Giardia trophozoites. The results showed that the three medical solutions had a certain inhibitory effect onGiardia. The IC₅₀ of Combretum indicum alcohol extracts was 1.06 mg/mL; the IC₅₀ of Combretum indicum water extracts was 8.145 mg/mL, and the IC₅₀ of metronidazole was 0.325 mg/mL; and the shortest time to IC₅₀ was 5.28 h, 5.95 h and 3.85 h, respectively. At IC₅₀ concentration, when incubated for 6 h or more, there was no significant difference in the Giardia concentration between the Combretum indicum alcohol extracts group and the metronidazole control group（P＞0.05）. During the entire culture period, the Giardia concentration in Combretum indicum water extracts group was significantly higher than that in metronidazole control group（P＜0.05）. After 6 h of action of Combretum indicum alcohol extracts, the trophozoite body was deformed, and the flagella were damaged. After 12 h of action, the cell membrane ruptured; the cell contents overflowed; part of the structure of the suction cup microtubules disintegrated, and trophozoites began to die. The results suggested that Combretum indicum had the effect of inhibiting the growth of Giardia, and the alcohol extracts had a stronger inhibitory effect than water extracts, which was concentration dependence. The IC₅₀ concentration of Combretum indicum alcohol extracts was comparable to metronidazole on inhibition effect of Giardia.