INTRODUCTION
Oxidative stress is initiated by reactive oxygen species such as hydrogen peroxide (H2O2), peroxyl nitrite, as well as hydroxyl radical (.OH), superoxide anions (O2-), nitric oxide (NO.) which seek stability through electron pairing with biological macromolecules such as proteins, lipids and DNA in healthy human cells and cause protein and DNA damage along with lipid peroxidation (Hazra et al ., 2008). These changes contribute to cancer, ageing, inflammation and cardiovascular disease such as atherosclerosis (Suja et al .,2016; Hazra et al .,2008; Braca et al .,2002). Atherosclerosis is a multifactorial complication leading to heart attack and stroke. Oxidation of low density lipoproteins (LDL) has been suggested to be an initial step in the development of atherosclerosis (Naidu et al ., 2001). Oxidized LDL is taken up by macrophages at an enhanced rate via their scavenger receptors (Aviram et al ., 2000; Parthasarathy et al .,1986), leading to the formation of lipid-laden foam cells, the hallmark of the early atherosclerosis (Aviram et al .,2000; Berliner et al .,1995).
Antioxidants with free-radical scavenging activities could have great importance as prophylactic and therapeutic agents in diseases in which oxidants or free radicals are implicated (Vikas et al .,2017; Marnett et al ., 2000). The most common antioxidants currently in use include BHA- Butylated hydroxyl anisole, BHT Butylated hydroxyl toluene, propyl gallate, and tert-butyl-hydroquinone (Gulcin et al .,2004). However, they have been suspected to be responsible for liver damage and carcinogenesis in laboratory animals (Biswas et al .,2010). Therefore, the research on the development of the new, safe and effective antioxidants are nowadays vivaciously encouraged and botanicals might be the alternative solution.
Plecthrantus glandulosus Hook. F. (Lamiaceae) is one of natural products with culinary applications and health benefits. It is a climbing herbaceous plant widely distributed in West, Central and South of Africa (Pele et al .,1986). It is used in Cameroon’s traditional medicine to treat dermatitis, bellyache, venereal diseases, internal inflammation, lower abdominal and nerve ache. Known as Ava in Ewondo, the plant is used as condiment in the Ewondo tribe (Peleet al .,1986). Earlier studies reported the antinociceptive and anti-inflammatory effects (Fongang et al .,2016) as well as antioxidant and insecticidals activities (Danga et al . 2014; Danga et al ., 2015; Goudoum et al .,2009). As phytochemical constituents of P. glandulosus , one new methoxylated flavonoid derivative, plectranmicin and one new monoterpene derivative, plectranmicinol, together with seven known compounds including 5-hydroxy-3,7,2′,4′tetramethoxyflavone; 5,7-dihydroxy-3,2′,4′-trimethoxyflavone; 7-hydroxy-5,6,4′trimethoxyflavonen; 3-epi-betulinicacidn; 3O-β-D-glucopyranosylstigmasterol; β-sitosterol and 4-epi-fridelin were isolated from the whole plant (Tsopmejio et al in 2019).
The present study was undertaken to evaluate the in vitroantioxidant properties of the leaves extracts and fractions as well as their protective effects against human low density lipoprotein oxidation induced by copper sulfate (CuSO4).