This efficacy of administering increasing dosages of mango seed extract resulting on the reduction of epg counts may be attributed to the anthelmintic components present in the mango seeds. Mango seed kernel extracts have been shown to contain tannins, flavonoids, alkaloids, saponins, and glycosides [10]. Extracts have been reported to exhibit a wide range of activities such as antioxidant, antimicrobial [11], antifungal [12], antidiarrheal [13], antiproliferative against colon cancer cells [14], and tyrosinase inhibition [15].
The mango seed has been considered a good source of polyphenols. For Egyptian mango Hindi cultivar, a significant amount of phenolics and flavonoids are present in mango seed kernel extracts at 17,400 and 3,325 mg per 100 g seed [16]. Similarly, among three Chinese mango cultivars, the kernels contained 15.5 mg of gallotannins per g dry matter [17]. Kernels of the Ubá variety from Brazil contained 82,540 mg per kg dry matter [18]. Across these studies, it was observed that the mango seed kernel contained the highest amounts of phenolics compared to the pulp and peel, making it a promising source of polyphenolics.
Gallates and gallotannins are the major family of compounds present in the mango seed kernel extract. Gallotannins are hydrolyzable tannins that contain gallic acid substituents [19]. When hydrolyzed by acids and under physiological conditions in the gastrointestinal tract, these gallotannins may release gallic acid [20]. Most studies report the role of condensed tannins related to anthelmintic activity. However, hydrolyzable tannins are reported to exhibit similar anthelmintic activity with that of condensed tannins. Extracts containing only hydrolyzable tannins have similar activity with extracts which have both condensed and hydrolyzable tannins and can even have higher anthelmintic activity than extracts containing only condensed tannins [21]. Gallotannins isolated from Camelia sinensis have shown strong anthelmintic activity against Caenorhabditis elegans [22]. Moreover, condensed tannins with gallic acid units had higher anthelmintic activity compared to that with no gallic acid units [23].
The anthelmintic activity of hydrolyzable tannins is mainly egg hatching and larval migration inhibition while condensed tannins only exert minor effects on egg hatching. This implies that hydrolyzable tannins have a different mode of action for its anthelmintic activity [24]. It was shown that the size of the hydrolyzable tannins, overall flexibility, type and number of functional groups, and the linkages between the monomeric hydrolyzable tannins had different effects on the activity [25, 26]. Particularly, the molecular size and the number of free hydroxyl groups seem to be crucial elements for anthelmintic activity [8]. This may be due to the difficulty of larger molecules to permeate into target cells or within the parasite. In contrast, smaller molecules will be able to move easily and bind with target molecules.
In addition to hydrolyzable tannins, mango seed kernel also contain a substantial amount of flavonoids, which may have also contributed towards the reduction of epg counts. It is hypothesized that flavonoids have a mode of action similar to that of tannins. This means that flavonoids may interfere with the biology of the nematodes through egg hatching or larval motility inhibition such as the activity shown by sainfoin against Haemonchus contortus [27]. Though in smaller amounts, the alkaloids present may also have anthelmintic effects. Alkaloids have been reported to inhibit egg hatching [28] and may have the ability to intercalate with DNA synthesis of parasites [29].
Aside from the mango seed kernel, studies have shown that other parts of the mango have anthelmintic activity. Immature mango fruits have shown high in vivo efficacy yet moderate anthelmintic action against nematodes, particularly H. contortus, in sheep [30]. However, it was not reported as to what may have caused the activity nor the decrease in activity when it was tested in vivo. In contrast, this study was able to exhibit a strong anthelmintic action in vivo. This is largely due to the difference of the metabolism between sheep and pig but may also be due to the amount of the active substance in different parts of the mango. This study shows that the mango seed contains significant amounts of bioactive compounds enough to have an efficacy similar to a commercial anthelmintic.