Opuntia spp. (cactus) belong to the most abundant cactus plants and are widely distributed across the globe. Besides the American continent, cactus plants from Opuntia spp. Are present in various regions of Africa, Europe, and Asia. They are especially abundant in arid and semi-arid regions although they may grow in various environments from tropical (> 5° C) to cold (< -40° C) areas, and from sea level to high altitudes (4500 m above sea level). About half of the total number of known Opuntia species are present in Mexico and they constitute an important component of the Mexican diet since some cladodes (cactus pads) from particular species (e.g. Opuntia ficus-indica, Opuntia megacantha) are edible and can be obtained easily from cultivars or in the wild. In addition, fruits from Opuntia spp. can also be harvested and consumed and represent an excellent source of sugars, fibers, and antioxidants. They are often processed to prepare smoothies, popsicles, flavored water, etc.
In this thesis of Herson Antonio Gonzalez Ponce, we evaluated the protective effect of the consumption of fruit juices from Opuntia robusta and Opuntia streptacantha species, obtained from a semi-arid region of Aguascalientes, México, against acute liver toxicity induced with acetaminophen (APAP) and diclofenac (DF). These analgesics are responsible for most cases of direct or idiosyncratic acute liver failure (ALF) and death around the world by the inappropriate use of over-the-counter (OTC) analgesics or non-steroidal anti-inflammatory drugs.Lyophilized extracts from fruits were prepared and stored until their use in in vivo and in vitro models. The antioxidant capacity and the main bioactive components of the fruit extracts were determined by spectrophotometric and chromatographic techniques. Results indicated that Opuntia robusta fruit extracts have a greater antioxidant capacity and contain higher amounts of phenolic compounds, flavonoids, and betalains (betacyanins and betaxanthins) as well as higher amounts of betacyanins (betanin and isobetanin) than Opuntia streptacantha fruit extracts. To induce acute liver damage, APAP and DF were used at 500 mg/kg and 75 mg/kg, respectively for the in vivo experiments and 20 mmol/L and 400 µmol/L for the in vitro experiments, using primary cultures of rat hepatocytes. Biochemical, histological, and molecular techniques were performed to evaluate the protective effects of the Opuntia juice extracts against APAP and DF-induced liver toxicity. The main findings were that Opuntia robusta fruit extract significantly reduced the main biochemical markers of liver damage (ALT and AST), preserved normal cytoarchitecture of the hepatic parenchyma, reduced focal necrosis at zone 3 of the hepatic lobule, prevented mitochondrial dysfunction that triggers cell death, promoted the activation of the antioxidant enzymes HO-1 and GCLC, and increased the expression of the survival and stress sensor Gadd45β compared to Opuntia streptacantha fruit extract. These effects were notable both in the in vivo and the in vitro model and in both APAP- and DF-induced liver toxicity. Our results suggest that Opuntia fruit extracts are a valuable resource of hepatoprotective compounds. Further studies to identify the biologically active components of these extracts as well as standardization of extraction, the optimal dose, and administration, are needed.
