Efficacy
The anti-malarial activity of omidun, used in traditional medicine in Nigeria and elsewhere in suppressive, curative and prophylactic mice test models are reported. The study revealed a good parasitaemia reduction in the curative and suppressive group while the prophylactic group had no reduction in parasitaemia values. This is indicative of the high anti-malarial potentials of omidun, which is also greatly dependent on its usage.
The pattern of reduction in the parasitaemia levels of the
omidun curative group is consistent with the positive control group where chloroquine was administered and in contrast to the negative control where no treatment was administered, causing a consistent increase in the parasitaemia levels of the animals. The curative
omidun treatment shows a significant difference statistically (p < 0.05) with that of the negative control groups while showing no statistical significant difference with the positive control group, chloroquine, i.e., the effect of
omidun is highly similar to that of chloroquine but differs greatly from the untreated group. This is similar to the study carried out by Berthi et al. [
15] on the anti-plasmodial effect of plant extracts from
Picrolemma huberi and
Picramnia latifolia where
Picrolemma huberi had a good reduction in parasitaemia levels consistent with the chloroquine treatment, which was also used as the positive control.
In the prophylactic study, it was observed that the parasitaemia level of the
omidun group on the 5th day (day 4) immediately after the prophylaxis administration was very low (0.78%) compared to that of the positive (1.54%) and negative control (2.18%); this suggests that the
omidun was able to prevent the appearance of the parasite in the blood. However, the parasitaemia level of the test group increased greatly on the 8th day (day 7) due to stoppage in administration of the
omidun, suggesting that the LAB and its metabolites present in the
omidun might have been cleared from the animal, thus preventing the anti-malarial effect to remain and accounting for the rise in the parasitaemia level. This is similar to the study by Misganaw et al. [
16] on the evaluation of the anti-malarial activity of crude extract and solvent fractions of the leaves of
Olea europaea (Oleaceae) in mice where it was observed that in the prophylactic test, the extract produced the lowest percentage suppression of parasitaemia compared to its effect in the curative and suppressive group, which however demonstrated significant suppressive effect on the level of parasitaemia compared to the negative control group. This finding is in agreement with the studies carried out by Unekwuojo et al. [
17] on the suppressive, curative and prophylactic potentials of
Morinda lucida (Benth) against erythrocytic stage of mice infected with chloroquine-sensitive
P. berghei where the prophylactic treatment had the lowest parasitaemia reduction. It can thus be said that the effectiveness of the
omidun lies in its continuous use until the parasite is completely eradicated.
The suppressive treatment of
omidun revealed that there was total suppression of parasites in the blood stream of the animals just as was also observed in the chloroquine treatment group. Parasites were however seen in the group treated with normal saline (negative control) where the parasitaemia level increased from 1.46 to 3.34%. This suppressive
omidun treatment shows a statistical significant difference with that of the negative control groups while showing no statistical significance with the positive control group. This means that the effect of
omidun is highly similar to that of chloroquine but differs greatly from the untreated group. This is similar to the result obtained by Godwin et al. [
18] in the anti-malarial study of
Verbena hastate. The total absence of parasite in the suppressive group for the
omidun treatment revealed that the simultaneous administration of the
omidun and the parasite and the continuous treatment with
omidun hindered the appearance of the parasite in the blood stream consistent with the positive control and in contrast to the negative control. A similar result was reported by Jackie et al. [
19] where
Croton macrostachyus stem bark ethyl extract had 100% chemoprotective activity against malaria. This implies that
Omidun is efficacious in suppressing the appearance and survival of malarial parasite in the blood stream when there is a regular and continuous usage.
The
omidun curative and suppressive treatment was found to exert 100% parasite clearance from the blood stream of animals, it can therefore be said that
omidun has very good anti-malarial activity. This anti-malarial activity was classified according to Rasoanaivo et al. [
20] classification which states that extracts with very good or good activity should have 90–100% parasitaemia inhibition, extracts with good to moderate activity should have 50–90% inhibition, extract with moderate to weak activity should have 10–50% inhibition and extracts that are inactive have 0% inhibition.
This observed anti-malarial activity of
omidun in the curative and suppressive group is consistent with the traditional use of this liquid as a solvent for herbal medications against malaria and indicative of its potential as a chemotherapeutic anti-malarial agent even when used alone without herbal compounds. The anti-malarial activity of
omidun may be attributed to the high level of LAB present in it with their various metabolites [
7], which have been shown to have rich nutritional benefits, health values, antimicrobial activity, and even antiplasmodial potentials [
21].
LAB synthesizes antimicrobial peptides (AMPs), generally known as bacteriocins, to enable successful existence and enhance protection against pathogens [
22,
23]. AMPs are showing potential as powerful weapons against bacteria, fungi and parasites considering their inhibitory spectrum. AMPs LR14 is a multi-peptide bacteriocin that has been purified from
Lactobaccilus plantarum and has been investigated for activity against human pathogen
Plasmodium falciparum [
22].
Krugliak et al. [
24] reported the anti-malarial effects of C18 fatty acids on
P. falciparum, Plasmodium yoelii nigeriensis and on
Plasmodium vinckei petteri in vivo, stating that the C18 acids displayed a considerable and rapid inhibition of these parasites. Soh et al. [
25] showed that ellagic acid had high activity in vitro against all
P. falciparum strains regardless of their level of chloroquine and mefloquine resistance. The authors further reported that this acid was active in vivo against
P. vinckei petteri in suppressive, curative and prophylactic murine tests without any toxicity. Moneriz et al. [
26] reported the parasitostatic effect of maslinic acid.
It is important to note that the many properties of
omidun could also be linked to the important contribution of LAB present in
omidun with their metabolites. LAB possess the ability to boost the immune system and decrease the danger of diseases [
27,
28] and to assist quicker recovery from sickness [
29]. In addition, fermented foods such as
omidun contain vitamin C, iron or zinc, which have been shown to help strengthen the immune system [
30]. LAB also produce organic acids in the course of growing which are secreted into the surroundings and they possess antimicrobial properties [
31].
Safety
The liver is highly essential in the assessment of internal damages due to malaria infections. This is because the liver plays a vital role in the survival of
Plasmodium cells [
32]. It is highly important that a good anti-malarial agent possesses the ability to completely clear parasites from the liver and aid the immune system in conducting necessary internal repairs in a short time [
32]. The
omidun treatment group was found to be void of visible lesions in the kidney for the curative group but with severe diffuse cord atrophy in the liver. This shows that
omidun treatment was completely unable to ameliorate damage done in the liver by the parasite, but it had little ameliorating effect as there was no necrosis recorded, in contrast to the untreated group that recorded severe diffuse cord atrophy and hepatocellular necrosis. However, no visible damage was observed in the kidney of the treated group, which indicates the non-toxicity of
omidun treatment in this group. This is in resonance with histopathological examination done by Berthi et al. [
15] of anti-plasmodial effect of plant extracts from
Picrolemma huberi and
Picramnia latifolia where the liver of mice treated with
Picrolemma huberi was observed to have a slight increase in hepatocyte nucleus size, binucleation, congestion and macrophages while the kidney had no visible damage. The chloroquine treatment for the curative group showed moderate centrilobular hepatocellular vacuolar degeneration in the liver of the animal; this also shows that chloroquine treatment was completely unable to ameliorate damage done in the liver by the parasite but it had little ameliorating effect as there was no necrosis recorded, in contrast to the untreated group that recorded severe diffuse cord atrophy and hepatocellular necrosis. The kidney of this group however exhibited tubular epithelial degeneration and necrosis, which indicates the toxicity of chloroquine, and this is likely a reason why withdrawal from chloroquine and shifting to another form of treatment is advised [
33].
In the prophylactic group, the
omidun treatment revealed moderate diffuse cord atrophy and centrilobular coagulation necrosis in the liver while the kidney had necrosis of tubular epithelial cells and interstitial inflammation. This could be linked to the damaging effect of the parasites as
omidun was unable to clear parasites in this group. The chloroquine treatment revealed moderate centrilobular hepatocellular atrophy and accentuation of sinusoids in the liver while the kidney had no observable lesion. Okpok et al. [
34] attributed the damage of organs recorded in that study to a feature of severe
Plasmodium infection or a characteristic of tissues previously exposed to parasitic infection.
In the suppressive group,
omidun treatment revealed diffuse atrophy of hepatocytes and cord in the liver while the kidney of the animal had no observable lesion. The chloroquine treatment revealed moderate diffuse hepatocellular atrophy and accentuation of sinusoids in the liver of the animal while the kidney had necrosis of tubular epithelial cells and interstitial inflammation. This agrees with the study carried out by Diwan et al. [
35] where histological changes was observed in the organs of mice treated with saponin extracted from
Citrullus colocynthis plant.
Omidun and chloroquine treatment was able to suppress the upset of parasite in the blood stream of the animal, it is expected that there would be no damage in the liver caused by the parasite, therefore damage observed in the liver of the animal may have arisen from other factors. This hypothesis is confirmed by the presence of damage in the liver of the animals that were uninfected and untreated. The toxicity of
omidun can be said to be very low as there was no observable lesion in the kidney of the animals in this group.
The uninfected group but administered with chloroquine had severe diffuse cord atrophy and hepatocellular necrosis in the liver with tubular epithelial necrosis and inflammation in the kidney. The group administered with omidun without infection showed that the liver had random hepatocellular vacuolar degeneration while the kidney had no visible lesion; this indicates lesser toxicity than that of chloroquine as there was no necrosis recorded in the liver and no observable damage in the kidney.
The uninfected and untreated group showed that the liver had moderate diffuse vacuolar degeneration of the hepatocytes while the kidney had no visible lesion. This implies that the damage observed in the liver of treated groups may not have resulted from either the omidun or chloroquine since the group that was not administered with any treatment still revealed damage in the liver which could be linked to other factors, such as stress, fatigue, nutrition, atmospheric condition, and immune status of animals.