Essential oils are potential therapeutics for coronavirus disease 2019 (COVID-19), in which some of the volatile compounds of essential oils have been well known for their broad antiviral activities. These therapeutic candidates have been shown to regulate the excessive secretion of pro-inflammatory cytokines, which underlies the pathogenesis of severe COVID-19. We aimed to identify molecular targets of essential oils in disrupting the cell entry and replication of SARS-CoV-2, hence being active as antivirals. Literature searches were performed on PubMed, Scopus, Scillit, and CaPlus/SciFinder (7 December 2022) with a truncated title implying the anti-SARS-CoV-2 activity of essential oil. Data were collected from the eligible studies and described narratively. Quality appraisal was performed on the included studies. A total of eight studies were included in this review; four of which used enzyme inhibition assay, one—pseudo-SARS-CoV-2 culture; two—whole SARS-CoV-2 culture; and one—ACE2-expressing cancer cells. Essential oils may prevent the SARS-CoV-2 infection by targeting its receptors on the cells (ACE2 and TMPRSS2). Menthol, 1,8-cineole, and camphor are among the volatile compounds which serve as potential ACE2 blockers. β-caryophyllene may selectively target the SARS-CoV-2 spike protein and inhibit viral entry. Other interactions with SARS-CoV-2 proteases and RdRp are observed based on molecular docking. In conclusion, essential oils could target proteins related to the SARS-CoV-2 entry and replication. Further studies with improved and uniform study designs should be carried out to optimize essential oils as COVID-19 therapies.

Increasing production of cocoa (Theobroma cacao L.) leads to a higher environmental burden due to its solid waste generation. Cocoa pod husk, one of the major solid wastes of cocoa production, contains rich bioactive compounds unveiling its valorization potential. With that in mind, our research aimed to explore the biological and antioxidant activities of aqueous extracts from cocoa pod husks. In this present work, cocoa pod husk was extracted using water and subsequentially partitioned using n-hexane, ethyl acetate, and methanol. The antimicrobial investigation revealed that the ethyl acetate solubles were active against the Staphylococcus aureus, Escherichia coli, and Candida albicans, where at a 20% w/v concentration, the inhibition diameters were 6.62 ± 0.10, 6.52 ± 0.02, and 11.72 ± 0.36 mm, respectively. The extracts were found non-toxic proven by brine shrimp lethality tests against Artemia salina with LC₅₀ scores ranging from 74.1 to 19,054.6 μg/mL. The total phenolic content and total flavonoid content were obtained in the range of 47.44 to 570.44 mg/g GAE and 1.96 to 4.34 mg/g QE, respectively. Antioxidant activities of the obtained extracts were revealed by 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) assay with EC₅₀ reached as low as 9.61 μg/mL by the ethyl acetate soluble. Phytochemical screening based on gas chromatography—mass spectroscopy analysis on the sample with the highest antioxidant activities revealed the dominant presence of three phytosterols, namely gamma-sitosterol, stigmasterol, and campesterol.

Essential oils are thought as potential therapies in managing coronavirus disease 2019 (COVID-19). Many researchers have put their efforts to tackle the pandemic by exploring antiviral candidates which consequently changes the research landscape. Herein, we aimed to assess the effect of COVID-19 pandemic toward the landscape of essential oil research. This study employed bibliometric analysis based on the metadata of published literature indexed in the Scopus database. The search was performed on December 15^th, 2022 by using keyword ‘essential oil’ and its synonyms. We grouped the data based on publication year; pre-COVID-19 (2014–2019) and during COVID-19 (2020–2024, some studies have been published earlier). Further, we separated the COVID-19-focused research from COVID-19 (2020–2024) by introducing a new keyword ‘COVID-19’ during the search. All metadata were processed using VoSviewer and Biblioshiny for network visualization analysis. Selections of frequently occurring keywords, clusters of keyword co-occurrence, and the list of most impactful papers were performed by two independent reviewers. Metadata from a total of 35,262 publications were included for bibliometric analysis, comprised of three groups of datasets namely pre-COVID-19 (n = 18,670), COVID-19 (n = 16,592), and COVID-19-focused (n = 281). Five research topics clusters were found from pre-COVID-19 dataset, eight – from COVID-19 dataset, and nine – from COVID-19-focused dataset. COVID-19 cluster containing the keyword ‘antiviral’ emerged in the COVID-19 dataset, whereas none of the previous research topic clusters contained the keyword ‘antiviral’. Antiviral, angiotensin-converting enzyme 2 (ACE2) inhibitory, and anti-inflammation activities were among the top occurring keywords in studies covering both essential oil and COVID-19. Studies on essential oil used for managing COVID-19 were most reported by authors from the United States (documents = 37, citations = 405), Australia (documents = 16, citations = 115) and Italy (documents = 23, citations = 366). A significant increase was found during COVID-19 pandemic for publications covering essential oil themes, but only a small portion was occupied by COVID-19 research. The COVID-19 pandemic does not alter the ongoing progress of essential oil research but rather offers a new spotlight on the antiviral potential of essential oils. Hence, the COVID-19 pandemic has provided an opportunity to investigate deeper the antiviral potential of essential oils.

Rhizophoraceae is a large true mangrove family that produces mangrove tannins. Tannins have the potential to be used as antimutagenic, anticancer, antimicrobial, and antioxidant agents in the pharmaceutical and medical fields. The aim of the research was to determine the total tannin content, antimicrobial activity, and the correlation between the two in methanol extracts of four plant parts (roots, bark, leaves, and fruit/hypocotyl) from five Rhizophoraceae species, namely Bruguiera cylindrica, Bruguiera gymnorrhiza, Ceriops decandra, Rhizophora apiculata, and Rhizophora mucronata originating from the Langsa mangrove forest, Aceh, Indonesia. Folin Ciocalteu colorimetric method and tannic acid as a standard were used for the total tannin content (TTC) test. The disc diffusion method was used to conduct antimicrobial tests against Escherichia coli, Staphylococcus aureus, and Candida albicans bacteria at a 50% extract concentration. TTC content in Rhizophoraceae ranged from 8.17 ± 1.36 mg TAE/g to 813.35 ± 18.72 mg TAE/g (p < 0.05). The highest levels were found in C. decandra roots (813.35 ±18.72 mg TAE/g), C. decandra bark (704.36 ± 12.11 mg TAE/g), and R. apiculata bark (651.23 ± 2.36 mg TAE/g). The extract has moderate to strong antibacterial activity against gram-positive bacteria S. aureus, with an inhibition zone range of 6.64 ± 0.80 mm -15.02 ± 0.32 mm. The highest antibacterial activity was observed in the inhibition zones for S. aureus bacteria, with C. decandra fruit extract (15.02 ± 0.32 mm), R. apiculata bark (14.78 ± 0.90 mm), and C. decandra leaves (14.44 ± 1.18 mm) exhibiting the highest levels. TTC and antibacterial activity of S. aureus in Rhizophoraceae extracts showed a moderate correlation (Pearson correlation coefficient r = 0.566, p < 0.05). According to the results, it was concluded that Rhizophoraceae has the potential to produce optimal tannins that can be used as antibacterial agents against S. aureus.

Nutmeg plant (Myristica fragrans Houtt) is known as one of traditional medicine. The nutmeg root has a strong potential in antioxidant and anticancer agents among other nutmeg plant parts. The n-hexane root extract has been carried out by thin-layer chromatography and obtained 8 fractions (labeled as Myristica fragrans Houtt Root: MFHR 1 − 8). Specifically, the MFHR 4 has been purified for several times to obtain a yellow-brown color. Furthermore, lignan compound 6′-methyl-(7‑hydroxy-8-methylbut-9-en)-3,2′-dimethoxybiphenyl-4,5-diol) was identified with chemical formula of C20H24O5 and analyzed using UV–vis spectroscopy, fourier-transform infrared spectroscopy (FTIR), 1D/2D nuclear magnetic resonance (NMR), and liquid chromatography–mass spectrometry (LC-MS). Based on MTT assay, MFHR demonstrated moderate anticancer activity against MCF-7 cell lines of 51.95 µM, meanwhile, DPPH activity confirmed the strong antioxidant activity with IC50 value of 12.67 ppm.

Polyurethane membranes are widely developed polymers by researchers because they can be made from synthetic materials or natural materials. Red seaweed (Gracilaria verrucosa Greville) is a natural material that can be developed as a raw material for polyurethane membranes. This study used red seaweed biomass (RSB) as a raw material to manufacture polyurethane as an adsorptive membrane for removing ammonia in water. The membrane composition was determined using the Box–Behnken design from Response Surface Methodology with three factors and three levels. In the ammonia adsorption process, the adsorption isotherm was determined by varying the concentration, while the adsorption kinetics was determined by varying the contact time. Red seaweed biomass-based polyurethane membrane (PUM-RSB) can adsorb ammonia in water with an adsorption capacity of 0.233 mg/g and an adsorption efficiency of 16.2%. The adsorption efficiency followed the quadratic model in the Box–Behnken design, which resulted in the optimal composition of RSB 0.15 g, TDI 3.0 g, and glycerin 0.4 g with predicted and actual adsorption capacities of 0.224 mg/g and 0.226 mg/g. The ammonia adsorption isotherm using PUM-RSB follows the Freundlich isotherm, with a high correlation coefficient (R²) of 0.977, while the Langmuir isotherm has a low R² value of 0.926. The Freundlich isotherm indicates that ammonia is adsorbed on the surface of the adsorbent as multilayer adsorption. In addition, based on the analysis of adsorption kinetics, the adsorption phenomenon follows pseudo-order II with a chemisorption mechanism, and it is assumed that the bond that occurs is between the anion –SO₄²⁻ with the NH₄⁺ cation to form ammonium sulfate (NH₄)₂SO₄ and between isocyanates (NCO) with NH₄⁺ cations to form substituted urea.