Oxidative stress is a devastating phenomenon that affects humans. An imbalance between the cellular production of reactive oxygen species and cells' ability to scavenge them is the culprit of an array of neurodegenerative, heart and several other age-related diseases . The reactive oxygen and nitrogen species, including superoxide (O2−), hydroxyl (OH), peroxyl (RO2), and alkoxyl (RO−), nitric oxide (NO−), peroxynitrite (ONOO−), nitrogen dioxide (NO2), cause oxidative damage of cellular components such as lipids, proteins and nucleic acids leading to cellular death either via necrosis or apoptosis . This catastrophe is a natural consequence of the biological production of energy, the severity of which can become more worsened due to depletion of cellular antioxidant defence systems .
All biological systems have evolved to possess inherent antioxidant defence mechanisms to counteract and protect against oxidative damages. However, there is often a need for the consumption of dietary antioxidants, especially during illnesses. Consequently, the use of naturally occurring phytochemicals, which are known to trigger antioxidant responses, has been proposed as a practical therapeutic approach for these chronic diseases .
Moreover, literature search also confirmed the efficacies of phytochemicals, antioxidants, and vitamins in the amelioration and treatment of complications from excessive oxidative stress [5, 6].
Farombi et al.  described antioxidants as compounds that can delay or inhibit the oxidation of biomolecules by inhibiting the initiation or propagation of oxidative chain reactions and which can thus prevent or repair the damage done to the body's cells by reactive oxygen species. Some of these phytochemicals, such as flavonoids from medicinal plants, have been reported to be safe while showing other pharmacological actions, in addition to their antioxidant properties, including anticarcinogenic, antimutagenicity, antibacterial, antiviral, and anti-inflammatory effects .
The plant Crotalaria retusa L., commonly known as Devil Bean, is used traditionally as both food and medicine. Its medicinal value was reported to prevent cough, dyspepsia, fever, cardiac disorders, stomatitis, diarrhoea, scabies and impetigo. Locally, people use an infusion of the plant for bathing children to treat skin infections and thrush .
Clerodendrum volubile P. Beauv. (Verbenaceae), also known as "magic leaf" or "white butterfly leaf", is native to Nigeria's southern part. The leaf's traditional usage includes treatment of arthritis, rheumatism, dropsy, swelling, oedema, gout, and pain . Cassava (Manihot esculenta Crantz), popularly called Mandioca and Tapioca, is a popular tropical staple of economic importance. The peel is a waste product majorly used as animals' feeds . The cassava tuber peel's biogas slurry was selected to see whether the Slurry would contain promising biotransformation products.
Previous works have explored the prophylactic use of plant-derived bioactive agents to treat chronic diseases such as diabetes mellitus, cancer and cardiovascular diseases. Amongst these classes of bioactive agents, the focus was on the anti-inflammatory and antioxidant properties of polyphenols found in various plants . Based on this background, this study was designed to investigate the phytochemical contents and antioxidant properties of ethanolic and hot water infusion extract of Crotalaria retusa L., Clerodendrum volubile P. Beauv., and Cassava (Manihot esculenta Crantz) Biogas Slurry.