Green synthesis of nano-silver particles from leaf and stem extracts of <i>Iboza</i> (<i>Tetradenia riparia</i>)

Abstract

Background: Secondary metabolites derived from plant extracts can be used in the reduction of metal salts into their respective nanoparticles using simple, environmentally friendly and cost effective green synthesis techniques. Metal nanoparticles have important applications in medicine and agriculture. The leaves of Tetradenia riparia (Iboza), an important medicinal species in South Africa, are reported to contain various terpenoids and pyrones which can be used in the reduction of silver nitrate (AgNO 3 ) to nano-silver particles. Materials and Methods: Fresh leaves and stems of Iboza were oven-dried, crushed, extracted in water and methanol and filtered followed by incubation with AgNO 3 . Synthesized nano-silver particles were characterised using ultraviolet visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and Fourier transform infrared (FTIR) spectroscopy. Results:The bio-reduction of metal ion to base metal was rapidly conducted in a single step and at room temperature and pressure. UV-Vis spectra showed the characteristic surface plasmon resonance band of the synthesized nano-silver particles at 410 nm for all extracts. SEM analysis revealed predominantly aggregated spherically-shaped nano-silver particles with a size range of 20-50 nm and an average diameter of 26 nm. The presence of elemental silver in the nanoparticles was confirmed by EDX at 3 keV. As revealed by FTIR analysis, the reducing agents included terpenoids and pyrones which were responsible for reducing and capping the nano-silver particles. Conclusion: Both methanol and aqueous-derived extracts of Iboza leaves and stems can be used to synthesize nano-silver particles. FTIR evidence suggests that the reduction of the silver ions and the synthesis of the nanoparticles may have been actioned by various terpenoid and pyrone compounds found in the plant parts.

Synthesis temperature and time affect size, distribution and bioactivity of Tetradenia riparia-produced AgNPs

“…A survey of the literature shows an increasing move towards the green synthesis of NPs using plant extracts [15][16][17][18][19]. We too have reported NP synthesis and characterisation in T. riparia [20,21], a plant used as traditional medicine in South Africa [22,23]. Importantly, Shaik et al [20,21] showed that methanol and aqueous derived NPs displayed similar FTIR spectra.…”

“…In the latter study, nanoplates (40 nm diameter) were found to be more toxic than nanoparticles (57 nm diameter), based on the decrease in growth and photosynthetic activities. The average diameter of the spherically shaped NPs synthesized from leaf extracts of T. riparia was 26 nm [20,21], hence, according to the literature, they are likely to be highly bio-active.…”

“…We too have reported NP synthesis and characterisation in T. riparia [20,21], a plant used as traditional medicine in South Africa [22,23]. Importantly, Shaik et al [20,21] showed that methanol and aqueous derived NPs displayed similar FTIR spectra. Hence, these studies provide evidence to support biogenic synthesis thereby eliminating the use of harmful organic solvents [13,24] for extraction.…”

“…The leaves of T. riparia are known to possess various phytocompounds such as pyrones and terpenoids [22,23,25]. These secondary metabolites are reported to contribute to the pharmacological effects of the leaf extracts, and are purported to have played a role in the reduction of aqueous silver ions to their respective nanoparticles [21].…”

Mosquito-Borne Diseases and Their Control Strategies: An Overview Focused on Green Synthesized Plant-Based Metallic Nanoparticles

“…), alkaloids, polyphenols, terpenoids, sugars, and many other biologically active phytocompounds are able to reduce metal ions very quickly [ 183 ]. The obtained metallic nanoparticles are then purified by centrifugation and the recovered pellet is dried in the oven [ 184 ].…”