It is well known that antimicrobials may act like killing agents or impede the growth of microorganisms. On the one hand, due to the extraordinary recombination capability of the microorganisms, the genetic materials undergo rapid mutagenic transformations that hinder metabolic processes such as cell wall formation, synthesis and transcription of proteins, thus leading to the development of resistance against the known antimicrobials or antibacterials in the case of bacteria. On the other hand, recent unwise use of antibiotics has also resulted in the multitude of pathogens to develop resistance to the commonly employed antimicrobials. Therefore, pollution due to microbes is becoming one of the major threats related to environmental sanitation and human health ultimately. As a consequence, there arises a compelling and dire need for the research and development of novel and high potential antimicrobials which should be benevolent by nature.
Now turning to the alternatives available for the above subject, recent literature has shown that nanoparticles based on carbon nanotubes, fullerenes, and graphene oxide possess appreciable antimicrobial activity against various strains . Of late, antimicrobial activities of carbon-based nanostructures are being interestingly investigated owing to their high surface to volume ratio, large inner volume, and for other unique physical and chemical properties. Therefore, technological developments towards the design and synthesis of carbon-based antimicrobials that too from waste biomass that will reduce microbial resistance and infection burden have zeroed-in recently. Falling in this line, the present work explores the prospects of utilizing zero-cost leaf biomass of Vitex negundo L. plant for deriving activated carbon for evaluating its antibacterial properties.
Generally decayed or decaying plant biomass poses eco-pollution as its water content, sugar, mineral, and proteins would favor exponential growth of microorganisms. Also, a lot of microorganisms breed before the biomass could get decomposed, eventually bringing out rotten smell thereby polluting the environment. Generally, decayed or decaying plant biomass pose environmental pollution as its sugar, mineral, protein contents, and water retention nature creates favorable conditions for proliferation of microorganisms.
Phytochemical constituents of medicinal plants have been considered to be a basic requirement in the discovery of potential medicines and remedies for various diseases in Ayurvedic and Nutraceutical research. Medicinal properties of any plant depend on the type of phyto constituents and nutritive elements as well as minerals. Medicinal plants are effective against various health problems due to their pharmacological efficacy which depends on their elemental concentrations . Speaking about Vitex negundo, only medicinal properties is more frequently researched. The whole plant is traditionally important because it has many therapeutic values. It has been reported to possess potential pharmacological properties like antiinflammatory, antirheumatic, and antibiotic, hepato protective, antioxidant, anticonvulsant, oxidative stress, snake venom neutralization, and antiallergic activities . The leaves of Vitex Negundo is used to treat sprain, headache, abdominal pain, tooth ache, asthma, cough, fever, boils, wounds, and ulcers due to its antiseptic, astringent, antiinflammatory, and antipyretic nature . Thus, it can be seen that Vitex negundo plant has intense medicinal values and literature is also enormous. Hitherto, research is being focused only on the phytochemical composition and medicinal values of the plant Vitex negundo. However, one or two reports on activated carbon derived from Vitex negundo bark, stem, and flowers are only available .
Thus, it is apparent that the phytomass (plant biomass) wastes which may not have economic benefits may wisely be utilized by transforming zero-cost phytomass into activated carbon, which doubles up its worth by minimizing the waste management cost and by appreciably providing inexpensive alternative to the existing high priced commercial functional carbons. Thus, plant wastes from multiple sources present cost free and renewable carbon resource for numerous applications such as in biomedical and pharmaceutical fields as antibacterial agent.
The study of natural compounds containing sulphur and nitrogen is interesting because of their significant antibacterial, antifungal, and anticancer activity . It can be shown later in this article that the biomass-derived activated carbon too has sulphur and nitrogen (in addition to carbon, hydrogen, and oxygen) which are present as organic functional moieties in its structure to explain the observed effect against the pathogens. During the past 5 years, not many articles have appeared in the literature describing the biological activities using biomass-derived activated carbon alone. But to cite a few examples, using groundnut shell, Yallappa et al.  have done a pioneering work in the regard above. Lakshmi et al. have elaborately reviewed activated carbon nanoparticles from biowaste as a new generation antimicrobial agents . It is interesting to know that the kitchen soot was once applied as an antimicrobial and called “old woman’s remedy . In that sense, Sheena et al.  have reported antimicrobial activity of carbon nanoparticles isolated from natural sources against pathogenic Gram-negative and Gram-positive bacteria. Sekaran et al.  have reported the preparation of mesoporous-activated carbon from rice husk by precarbonization at 400 °C, chemical activation using phosphoric acid at various temperatures and have immobilized Bacillus sp. in the mesoporous-activated carbon for the degradation of sulphonated phenolic compounds in wastewater. Karthik et al.  have prepared activated carbon from Tribulus terrestris and have shown activity against E. coli, B. subtilis, S. aureus, and K. pneumoniae. Shamsi et al.  have reported a clear zone of inhibition of carbon nanoparticles obtained from sandal wood bark against B. cereus, E. coli, C. violeceum, and P. notatum due to these nanoparticles. Dheepan et al.  have reported in vitro evaluation of antibacterial efficacy using passiflora foetida-activated carbon against a score of pathogens. All these reports conclude that carbon materials produced from biomass still has enormous potential for acting against various strains of bacteria and that extended research is needed for a commercial success in the near future. Therefore, it is definite that the research outcome will be a welcoming route for producing zero-cost phytomass-derived cheap and affordable carbon materials possessing favorable characteristics for the intended applications.
The present research paper accordingly covers the preparation of activated carbon from natural and green source namely the leaves of V. negundo plant, the zero-cost phytomass and the evaluation of antimicrobial activity against selected human bacterial pathogens like S. aureus, S. pyogenes (Gram-positive type), and E. coli, P. aeruginosa (Gram-negative type). It further provides an ideal method for the utilization of V. negundo plant for producing low-cost and multifunctional-activated carbon which can be produced in bulk. This work is an evidence of taking wastes-making products-turning them in to resources (circular economy), the opposite of the current setup of seizing resources-making products-turning them to wastes (linear economy).