Studies on the anthelmintic property of aminobenzylated mannich bases.

Studies were conducted on the anthelmintic property of about 15(e-h, 1e-1h, 2d-2f and 3e-3h) synthesized aminobenzylated Mannich bases bearing N-methyl piperazine using Indian earthworms Pheritima Posthuma against piperazine citrate as standard reference. Three concentrations of each compound (0.1, 0.2, 0.3% w/v) were studied, which involved the determination of paralysis and death time of the worms. The compound 1g exhibited the most significant anthelmintic activity among all the compounds screened against the worms as compared to standard drug.

INTRODUCTION

Diseases caused by helminth parasites in livestock continue to be a major productivity constraint, especially small rhminants in the tropics and subtropics. Infections by gastrointestinal helminth parasites of livestock are among the most common and economically important diseases of grazing livestock.[1] Various drugs used for the cure of helminth infections are triimidazoles, bithional, parabendazole, mebendazole, oxfendazole, niclosamide and piperazine etc. However, drugs like mebendazole have considerable side-effects such as mitotic arrest and apotosis etc., and the benzimidazole, imidazothiazole and macrocyclic lactones’ class of drugs have become a global phenomenon in gastrointestinal nematodes of farm animals, hence there is a need for an anthelmintic with lesser side-effects. Also, due to escalating costs of research and development and limited commercial attractiveness, investment in research for new drug development for tropical diseases is much less as compared to other diseases.

It is well documented in the literature that Mannich bases are known to possess pharmacologically proven therapeutic potentials[2] and they find application as antimicrobial,[3] antitubercular,[4] antimalarial,[5] anticancer[6] and local anesthetic drugs.[7] Though extensive research work has been reported on Mannich bases, relatively very little is known so far about aminobenzylated Mannich bases[89] of N-methyl piperazine and the literature review revealed that piperazine and related compounds are known to possess anthelmintic activity.[10] This enthused us to evaluate some of the synthesized[11-14] aminobenzylated Mannich bases [Figure 1] for anthelmintic property in the present study.

Figure 1

Schematic representation of compounds (e-h, 1e-1h, 2d-2f, 3e-3h)

Anthelmintic activity of the synthesized compounds

The study of anthelmintic activity was carried out according to the method of Ajaigeoba[15] using Indian earth worm Pheritima posthuma due to its anatomical and physiological resemblance with the intestinal round worm parasites of human beings.[1617] Pheritima posthuma of nearly equal size (8 ± 1 cm) were collected from waterlogged areas of fort lake in Mandya district, Karnataka, India for the present study.

MATERIALS AND METHODS

Preparation of sample solutions

The suspensions of the sample[18] (0.1%w/v, 0.2%w/v and 0.3%w/v) were prepared by triturating the compounds with distilled water and 0.5%w/v tween 80 and further transferred to a beaker labeled as 0.1%, 0.2% and 0.3% respectively, stirred for about 30 min at room temperature. The resulting solutions were then used for anthelmintic studies.

Method of testing

Fifty-five groups of approximately equal-sized (8 ± 1 cm) Indian earthworms Pheritima posthama consisting of six earthworms in each group were placed in Petri dishes (4” size) containing suspensions of specific concentration (0.1%, 0.2%, 0.3%w/v) at room temperature. Each group was treated with one of the following: control (0.5%w/v tween 80 in normal saline), piperazine citrate (0.1%, 0.2%, 0.3%w/v in normal saline) different concentration of compounds (0.1%, 0.2%, 0.3%) respectively.

The times taken for complete paralysis and death were recorded using a stopwatch. The mean paralysis time and mean lethal time for each sample was recorded (each reading was taken in triplicate). The time taken by worms to become motionless was noted as paralysis time and to note the death time the earthworms frequently applied with external stimuli by transferring them to a beaker containing hot water in order to check its mortality. The anthelmintic activities of the tested compounds on Pheritima posthuma (earthworm) are indicated in Table 1.

Table 1

Anthelmintic activity of compounds (e-h, 1e-1h, 2d-2f, 3e-3h)

RESULTS AND DISCUSSION

The results of the anthelmintic activity exhibited by title compound on Pheritima posthuma are shown in Table 1. A closer inspection of data from this table indicates that compound 1 g was found to possess markedly higher anthelmintic activity than other compounds compared with standard. But all the other compounds were found to possess an interestingly low level of anthelmintic activity, which is a noteworthy feature of the present study.