Leishmaniasis is a disease that almost always has a chronic course, and is caused by the protozoan of the genus Leishmania being a difficult disease to treat because it is not easy to diagnose, the use of medication with considerable adverse effects. Treatments have serious drawbacks regarding resistance, stability, safety, and low tolerance, in addition to the traces that remain in the patient who has suffered from this disease and the co-infections that occur in the course of the disease, affecting their self-esteem [1].
The classification of tegumentary leishmaniasis in Peru is: Andean cutaneous leishmaniasis, known as "uta"; Andean cutaneous-mucosal leishmaniasis; forest cutaneous leishmaniasis; and forest cutaneous-mucosal leishmaniasis, known as "espundia" [2].
"UTA" in Peru is produced by the agent Leishmania peruviana [3, 4]. Leishmania braziliensis, which is resistant to antimonials, causes destructive damage to the skin and mucosa [3, 4]. Treatment with antimonials and glucantime has side effects, which makes it difficult for the patient to adhere to the scheme since it has nephrotoxic and hepatotoxic consequences, as well as aplastic anemia [3].
There are drugs used as first-line treatment for leishmaniasis, called antimonials. However, this treatment may cause side effects inherent to the medication that sometimes make people abandon the treatment [5–7]. However, it is still necessary to find new molecules with biological activity that can work as a treatment for such infection, and plant extracts and metabolites are a promising option. The therapeutic use of medicinal plants supports pharmaceutical research to combat various pathogens. In this sense, P. guajava is a tree belonging to the Myrtaceae family, which has its origin in Latin America, has been used as a food and therapeutic agent, the root, bark, leaves, fruits, flowers and seeds are used for medicinal purposes, particularly in infusions and decoctions for use topical and oral using it in the treatment of diseases caused by the activity of pathogenic and/or opportunistic microorganisms, describing its use as an antidiarrheal, against Gram +, Gram negative bacteria and Candida albicans [8–12]. A previous study reported in P. guajava phenolic components, tannins, flavonoids, triterpenoids, saponins, glycosides [13]. Additionally, P guajava is a commercial plant for its fruit [14].
Previous studies have concluded that to extrapolate in vitro assays of substances against leishmaniasis, samples should be used in which the parasite is in a similar condition to when it infects humans, i.e. in its "amastigote" form [6, 7]. Promastigotes, which have a different function and form than the parasite found in mammals, can be used as a comparison group. In addition, working with intracellular amastigotes results in complex and costly procedures, and their application is often limited [7].
Through in vitro techniques, it has been possible to develop axenic amastigotes with free-living characteristics in the form of artificial cultures, which can have functions and forms similar to those of the parasites found in human cells. For this reason, this is useful to identify new substances against leishmaniasis [7]. Therefore, this study aims to measure the effect of ethanolic and aqueous extracts of Psidium guajava against axenic promastigotes and amastigotes of Leishmania spp.