Volume 20, Issue 2, 2020 April-June

Volume 20, No 2 Pages:
2020 April-June Articles: 2

Essential oils: a review on their salient biological activities and major delivery strategies

Essential oils are volatile, complex products of plants as secondary metabolites and include terpenes and their oxygenated derivatives, such as alcohols, aldehydes, esters, ketones, phenols and oxides. In recent years, out of 3000 essential oils obtained from plant origin only 300 essential oils have gained extensive attention for applications in various fields. In this review, we discuss the major biological activities associated with EOs as antimicrobial, antispasmodic, antioxidant, antiviral, anti-inflammatory, anthelmintic, insecticidal, antiparasitic, and cytotoxic agents. Different routes for delivery of essential oil along with the problems associated with essential oils like high volatility, low stability, permeability, bioavailability, poor water solubility, susceptibility to oxidation, decomposition, photosensitization and skin irritation are also highlighted. Furthermore, strategies to solve the mentioned problems are suggested by different nanoencapsulating systems. These include polymer-based nanocarriers, lipid-based nanocarriers and molecular complexes. It is believed that nanoencapsulation of essential oils will improve their therapeutic activity and delivery.

Screening of Callicarpa arborea and Hemigraphis alternata for antibacterial activity

Callicarpa arborea and Hemigraphis alternata are two medicinal plants claimed to have antimicrobial property in Indian traditional medicine. The methanol extracts of the stem bark of C. arborea and the leaves of H. alternata were prepared and tested for antibacterial activity using disk diffusion method. Four Gram-negative bacteria such as Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae and Salmonella typhimurium; and two Gram-positive bacteria such as Micrococcus luteus and Bacillus subtilis were used. C. arborea extract was effective against all the bacteria tested, while H. alternata did not show any inhibitory activity. These findings suggest that C. arborea is a good source of antibacterial compound.

The chronicles of coronaviruses: the electron microscope, the doughnut, and the spike

The advancement of medicine owes in large measure to a German engineer Ernst Ruska, whose invention of transmission electron microscope in 1931 won him the 1986 Nobel Prize in Physics, when it comes to infectious diseases. Encouraged by his physician brother Helmut Ruska to use the prototype instrument for the study of viruses, the course of virology was shifted to a different and unprecedented level. Virus could then be seen, identified and imaged. The University of Maryland happened to acquire an American model of transmission EM, the RCA EMU, using which the first structural study was done for the first known coronavirus (then was simply known as infectious bronchitis virus) in 1948. The virus was described as rounded bodies with filamentous projections. The magnification was not great and the resolution was poor. The study was followed by a series of studies using improved techniques and better EM spanning the next decade. An upgraded version RCA-EMU2A gave better images in 1957 and the virus was described as doughnut-like structure. Using Siemens Elmiskop, D.M. Berry and collaborators made the first high-resolution pictures in 1964. The thick envelope which gave doughnut-like appearance and filamentous projections reported before could be discerned as discrete pear-shaped projections called the spikes. These spikes form a corona-like halo around the virus, which were also seen in novel human viruses (B814 and 229E) that caused common colds. The discoverer of B814, David Tyrrell and his aid June Almeida, a magnificent electron microscopist, established that IBV, B814 and 229E were of the same kind of virus in 1967, which prompted to create the name coronavirus in 1968. This article further highlights the detail structural organisation of coronaviruses emanating from these pioneering research.