The field of nanotechnology mainly encompasses with biology, physics, chemistry and material sciences and it develops novel therapeutic nanosized materials for biomedical and pharmaceutical applications. The biological syntheses of nanoparticles are being carried out by different macro-microscopic organisms such as plant, bacteria, fungi, seaweeds and microalgae. The biosynthesized nanomaterials have been effectively controlling the various endemic diseases with less adverse effect. Plant contains abundant natural compounds such as alkaloids, flavonoids, saponins, steroids, tannins and other nutritional compounds. These natural products are derived from various parts of plant such as leaves, stems, roots shoots, flowers, barks, and seeds. Recently, many studies have proved that the plant extracts act as a potential precursor for the synthesis of nanomaterial in non-hazardous ways. Since the plant extract contains various secondary metabolites, it acts as reducing and stabilizing agents for the bioreduction reaction to synthesized novel metallic nanoparticles. The non-biological methods (chemical and physical) are used in the synthesis of nanoparticles, which has a serious hazardous and high toxicity for living organisms. In addition, the biological synthesis of metallic nanoparticles is inexpensive, single step and eco-friendly methods. The plants are used successfully in the synthesis of various greener nanoparticles such as cobalt, copper, silver, gold, palladium, platinum, zinc oxide and magnetite. Also, the plant mediated nanoparticles are potential remedy for various diseases such as malaria, cancer, HIV, hepatitis and other acute diseases.

Copper oxide (CuO) nanowires of diameter ∼30–50 nm were developed by an aqueous polymeric solution based electrospinning process and their structural, morphological, and electrochemical properties were studied with the aim to fabricate high performance supercapacitor devices. The wires consist of densely packed cuboidal particles of size ∼10 nm characterized by a low degree of crystal defects. Supercapacitor electrodes were fabricated on nickel foam substrates using 75 wt% CuO in 15 wt% conducting carbon and 10 wt% polyvinylidene fluoride. The supercapacitive properties of the electrodes were evaluated in a three-electrode configuration in aqueous electrolytes, viz. KOH and LiOH, employing cyclic voltammetry (CV), charge–discharge cycling (CDC) and electrochemical impedance spectroscopy (EIS). A record specific capacitance (C_S) is observed for the present electrospun CuO nanowires: C_S ∼ 620 F g⁻¹ in KOH and 581 F g⁻¹ in LiOH at a current density of 2 A g⁻¹ with a Coulombic efficiency of ∼100%. Compared with the previous results on the electrochemical stability of CuO nanostructures, the material electrospun using an aqueous polymeric solution showed a much higher operational stability (98% at the end of 1000 cycles and 92% at the end of 2000 cycles) owing to its superior crystallinity. The electrochemical properties of the electrodes were determined using EIS to validate the CV and CDC results.

Depression is the most common illness observed in the elderly, adults and children. Antidepressants prescribed are usually synthetic drugs and these can sometimes cause a wide range of unpleasant side effects. Current research is focussed on natural products from plants as they are a rich source of potent new drug leads. Besides Hypericum perforatum (St. John's wort), the plants studied include Passiflora incarnata L. (passion flower), Mitragyna speciosa (kratom), Piper methysticum G. Forst (kava) and Valeriana officinalis L. Harman, harmol, harmine, harmalol and harmaline are indole alkaloids isolated from P. incarnata, while mytragynine is isolated from M. speciosa. The structure of isolated compounds from P. methysticum G. Forst and V. officinalis L. contains an indole moiety. The indole moeity is related to the neurotransmitter serotonin which is widely implicated for brain function and cognition as the endogenous receptor agonist. An imbalance in serotonin levels may influence mood in a way that leads to depression. The moiety is present in a number of antidepressants already on the market. Hence, the objective of this review is to discuss bioactive compounds containing the indole moeity from plants that can serve as potent antidepressants.