Phytochemical and biological activity study of Annona atemoya.

Abstract

Primary liver cancer ranks as the sixth most commonly diagnosed cancer worldwide and is the third leading cause of cancer-related deaths. Hepatocellular carcinoma (HCC) is the most prevalent type, accounting for 75 to 85% of liver cancer cases, and is the second leading cause of cancer-related deaths. The primary risk factors for developing HCC include chronic hepatitis B or C infections, obesity, excessive alcohol consumption, smoking, exposure to aflatoxin-contaminated foods, and type 2 diabetes. In Australia, the incidence of HCC has increased nearly fourfold, from 1.8 to 7.7 cases per 100,000 people between 1982 and 2016. Systemic therapies for advanced HCC are required and natural products, such as herbal extracts or pure compounds have garnered attention from scientists as potential alternative anti-cancer agents. In recent years the Annona species have been the focus of much interest for their anticancer activities. In 1789, the Annonaceae family was catalogued by de Jussieu. It encompasses tropical and subtropical plants which are widespread in distribution across various continents such as Asia, South and Central America, Australia and Africa. The genus of Annona is one of 120 genera of the Annonaceae family and contains more than 119 species of trees and shrubs. Most species are found in tropical America, where over 105 species have been identified. Due to its edible fruits and medicinal properties, Annona is the most studied genus of Annonaceae family. To date, only a limited number of these species have economic value, including A. squamosa L. (sugar apple), A. cherimola Mill. (Cherimoya), A. muricata L. (guanabana or soursop), A. atemoya Mabb. (atemoya), a hybrid between A. cherimola and A. squamosa, A. reticulata L. (custard apple), A. glabra L. (pond-apple) and A. macroprophyllata Donn. Sm. (ilama). Phytochemically, several classes of secondary metabolites, including acetogenins, essential oils, alkaloids, terpenoids and flavonoids. The pharmacological activities of Annona species leaves and seeds include antibacterial, anticancer, antidiabetic and anti-inflammatory properties. Annona atemoya also known as the custard apple is a hybrid between two Annonaceae species: Cherimoya (Annona cherimola) and the sugar apple (Annona squamosa). It is widely cultivated in tropical and subtropical continents including north and south America, Asia, Africa and Australia. Despite becoming an increasingly important commercial fruit plant due to its’ creamy succulent flesh, compared to other Annonaceae species relatively few studies have investigated the phytochemistry and bioactivities of A. atemoya. Studies that evaluated A. atemoya extracts and its constituents were searched through the databases Scopus, PubMed and Embase from inception to June 2020. Constituents of A. atemoya include alkaloids, flavonoids, terpenes and acetogenins. The results of this systematic review indicate that the constituents of A. atemoya possess cytotoxic, anti-angiogenic, hypolipidemic, antioxidant, anti-inflammatory and neuroprotective activities. However, many of these studies are currently limited in quality and further phytochemical and pharmacological studies are required. The study began with the screening of the phytochemical constituents of various parts including leaves, fruit’s pulp, and seeds. Our initial findings indicated the presence of annonaceous acetogenins in the leaves of A. atemoya for the first time. Fifteen compounds were reported, eleven were acetogenins and four were alkaloids. Additionally, two compounds were isolated, and their structures and absolute configuration were determined by interpretation of the spectroscopic data and previous reported studies. The concentration of acetogenins in the hexane extract was very low compared to the ethyl acetate extract. Furthermore, the phytochemical investigations of A. xxii atemoya fruit and seeds have been screened in this project. The results of this study indicated the presence of annonaceous acetogenins in the fruit’s pulp of A. atemoya for the first time. Eighteen compounds were identified in both cultivars, sixteen acetogenins and two alkaloids. The seeds of both cultivars were the richest in acetogenins, with sixteen compounds identified (1-11 and 16 to 20), compared with the pulp, which contained five acetogenins (1, 2, 3, 8 and 16). For the seed, both cultivars indicated some similarities (2, 3, 6, 7, 8, 10, 11 and 16) with more compounds reported in the AP cultivar. Moreover, the concentration of acetogenins in the pulp was very low compared to the seeds, and all three extracts of seeds illustrated almost the same acetogenins with more compounds reported in the ethyl acetate extract. The biological activity of A. atemoya crude extracts were examined using Huh-7 cell line. Results from this study indicate that only two crude extracts, LH and SEY, displayed anti-cancer activity in Huh-7 cells, with IC50 values of 67.21 and 22.55, respectively. Both extracts exhibited a dose-dependent inhibition of cell viability within 24 hours, as assessed by the MTS assay. For the remaining crude extracts that did not demonstrate cytotoxic effects, their protective effects were studied against PA. Most of these extracts were found to block PA by increasing the levels of anti-apoptotic proteins like Bax and Bim, while reducing the levels of pro-apoptotic proteins such as Bcl-XL and Mcl-1.