Aloe barbadensis Miller is a globally known medicinal plant species, popularly known as Aloe vera. Aloe vera gel has various folklore and therapeutic applications such as antiulcerogenic, cardioprotective, wound healing, antibacterial, antioxidant, anti-inflammatory, antifungal, immunoregulatory, etc. After collecting the gel, rinds (peels) are thrown away as agricultural waste that might cause environmental pollution. Nevertheless, based on the available literature, a systematic phytochemical/phytoceutical investigation of the rinds has not been reported. On the other hand, two species of caterpillars, tobacco hornworm (Manduca sexta; Lepidoptera: Sphingidae) and fall armyworm (Spodoptera frugiperda; Lepidoptera: Noctuidae), cause substantial loss to crops and vegetables every year worldwide. We noticed that these caterpillars cause minimal damage to the Aloe vera plants compared to other crops and vegetables in the same field. Based on this observation, we hypothesized that the epicuticular wax potentially plays a vital role in herbivore defense as an effective chemical defense of A. barbadensis. As a part of our ongoing research related to identifying precious natural compounds from waste materials, we have carried out a bioactivity-guided cold extraction of the Aloe vera rinds in hexanes to isolate the waxy part of the rinds. This extract was mixed with an artificial diet to determine the insecticidal effect on the growth and development of these two species of caterpillars (tobacco hornworm and fall armyworm). We observed that the extract reduced the growth significantly that even killed the caterpillars. Further analysis identified the presence of insecticide(s) in that extract. Our findings show that Aloe vera rinds may be a sustainable and unlimited source of natural insecticide(s). Therefore, proper attention should be paid before throwing away this so-called ‘agricultural waste’.

Aloe vera rinds: An agricultural waste or a sustainable resource of natural insecticide(s)?

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