Liquid Metals, Binahong Leaf and Tyrosinase Inhibitors: Antibacterials in the Literature


Antibacterials and hand sanitizers have never before gained the public's attention or demand as much as they have in the face of COVID-19.

According to Global Cosmetic Industry, market analyst firm IRI reported that year over year, from March 22, 2019 to 2020, sales in liquid hand soap grew 198% and hand sanitizers grew 184%; in relation, vitamins grew 77%. IRI surveyed consumers and found that “[p]reventive health care products, like immunity, are trending higher than symptomatic products, as consumers look first to prevent illness. Cleaning products and hand sanitizers/​soap [are] also important to consumer self care practices.”

In consideration of this critical market need, we offer the following brief literature review of recent research relevant to hand sanitizers and antibacterials.

α-Pinene and Turpentine Antibacterial Gels

Wijayati, N., Widiyastuti, A, Mursiti, S. and Rakainsa, S.K.; IOP Conference Series: Materials Science and Engineering; available at:

Research presented in late 2019 at the International Conference on Applied Sciences in Padang, Indonesia, described the effects of α-pinene derived from turpentine oil and turpentine oil itself in hand sanitizer gels. According to the article abstract, disc diffusion showed turpentine oil had the highest antibacterial activity at an inhibition zone of 13.8 mm against Staphylococcus aureus and at 8.83 mm against Escherichia coli; α-pinene was the most effective at 2.2 mm against S. aureus and 2.34 mm against E. coli.

In vitro Assessment of Commercial Hand Sanitizers

Ayaz, F., Rauf, F., Azeem, R., Khan, M.A., Tahir, A. and Bibi, K.; Pure and Applied Biology

This study was designed to demonstrate the antibacterial efficacy of 15 commercially available hand sanitizers against S. aureus, E. coli, Staphylococcus epidermidis and Pseudomonas aeruginosa using disc diffusion. Efficacies were tested at two concentrations, 100% and 50%. Among the sanitizers tested, three were found to be most effective: Biotol = 75%, Antibacterial hand gel = 75% and Hiclean = 62.5%. Additional efficacies are described for Purell, Enliven, Lifebuoy, Rivaj, Carex, Safeguard, Blue+King, Dial, Dettol, Cool and Cool, Infectiguard and Newlife.

Binahong Leaf-infused Sanitizer Gel

Rahmasari, D., Hendradi, E. and Chasanah, U.; Jurnal Farmasi dan Ilmu Kesehatan; available at:

According to these researchers, binahong leaf (Anredera cordifolia) is a natural herb containing phenolics, flavonoids, saponins and steroid-terpenoids compounds. Here it was explored as a potential active for a hand sanitizer gel and tested against S. aureus. Disc diffusion confirmed its efficacy at inhibition zones of 6.02 mm, 6.24 mm and 6.55 mm—close to a positive control (9.15 mm). Physicochemical properties of the gel also also were assessed, including organoleptic, pH, viscosity and spreadability, and showed good results.

See related: Hand Sanitizer Insanity and Formulating By the Book

Magnetic-activated Antibacterial Liquid Metals

Elbourne, A., Cheeseman, S., ...Truong, V.K., et al.; ACS Nano;

This worked aimed to develop stimuli-responsive antimicrobial technologies in the fight against antibiotic resistance in biofilms. Described is a proof of concept using magnetically responsive gallium-based liquid metal (LM) droplets as antibacterial materials. The LM are exposed to a low-intensity magnetic field such that, when placed into contact with the biofilm, they physically change shape and develop sharp edges that rupture bacterial cells, providing antibacterial efficacy.

Tyrosinase Inhibitors as Antibacterials

Yuan, Y., Jin, W., ... Ziora, Z.M., et al.; European Journal of Medicinal Chemistry

According to this article abstract, tyrosinase is a copper-containing enzyme that catalyzes the biosynthesis of melanin; over the years, its intrinsic antibacterial activity also has been reported. Here, researchers review the antibacterial activity of natural and synthetic tyrosinase and provide a hypothesis for its potential mechanisms of action.

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