## 1 Introduction  
Nanoparticles (NPs) contain uniquely increased surface area to volume ratio [1], varied shapes [2], and enhanced surface chemistry [3, 4] in comparison to macro and microparticles. Their nanoscale size endows them with enhanced biological, chemical, magnetic, catalytic, optical, and electrical properties that render them highly reactive, versatile, and useful [5, 6]. Consequently, they have found multitudinous applications in agriculture, food, cosmetics, medicine, and other sectors. In agriculture, they recently found applications even in niche areas such as mushroom production where administration of their small doses has been demonstrated to rapidly improve mushroom yields, biological and economic yields [7], nutritional composition [8, 9], and substrate lignin biodegradation [8]. Conventionally, NPs have been synthesized using chemical methods that employ chemical substances as both stabilizing and capping agents [10; 11]. However, such methods have recently been criticized for their use of costly, harmful, and toxic substances with the potential to harm human health and the environment [12]. Consequently, the field of nanomaterials science has witnessed a rapid surge in interest in green (bio) synthesis of nanoparticles that have been hailed as being biologically safe, environmentally friendly, highly stable, and easily characterizable [13; 14]. Biosynthesis of NPs could be achieved by using biogenic materials such as microorganisms or plant extracts. However, the use of microorganisms entails some stringent procedures such as the high need for culture media, which might be expensive and time-consuming, pathogenicity, and non-feasibility of large-scale production [15]. Phyto-assisted synthesis of NPs and its utilization of plant extracts as sources of phytochemicals is an extremely practical and cheap method with enormous potential for expansion into the large-scale commercial generation of NPs [16]. Plant-derived biomolecules and metabolites contain functional groups that interact with metal ions, thus reducing their size into the nano range. In this connection, polyphenolic compounds including alkaloids, polysaccharides, amino acids, vitamins, and terpenoids have been reported to bio-reduce metal ions or metal oxides to zero valence metal NPs [17]. Specifically, flavonoids comprise numerous functional groups, particularly the hydroxyl (-OH) group, that mainly reduce metal ions in a single reaction into NPs and cap them, thus enhancing their stability and biocompatibility [18; 19; 20]. Furthermore, plant-assisted NPs synthesis kinetics is amply higher than in other biosynthetic approaches, and plants are preferred to microorganisms for green synthesis of NPs as they are non-pathogenic [11]. Numerous parts of plants including leaves [21; 22], flowers [23], fruits [24; 25; 26], as well as seeds, stems, roots, and whole plants [11] have been used to biosynthesize ZnO-NPs and other metal NPs. Orange Habanero pepper (_C. chinense_) is a perennial plant belonging to the Solanaceae family and native to Central America, Mexico [27], India, and most parts of Africa [28]. Its fruits are known for their extreme level of heat [27] and their abundant metabolites such as ascorbic acid, phenolic compounds, vitamin A, and carotenoids [29]. Since the fruits possess these desirable phytochemicals, it is therefore hypothesized that their extract can act as a stabilizing agent during the biosynthesis ZnO-NPs. As part of attempts to investigate the utility and ensure the safety of NPs, it has become necessary to determine their deleterious effects on biological systems [30; 31]. Many nanomaterials including ZnO-NPs have been shown to be cytotoxic due to their ion-shedding ability [32; 33; 34] and high solubility in acidic conditions [35; 36]. ZnO-NPs intracellularly increase dissolved free zinc ions which disturbs metal ion homeostasis leading to mass production of reactive oxygen species (ROS) [26; 37; 38; 39] that cause oxidative stress [27] and inflammation [40].