Centaurea polyacantha and C. maroccana: the chemical composition of the aerial parts essential oils of these Centaurea species (Asteraceae) collected in Morocco

In the present study, the chemical composition of the essential oil from the aerial parts of two Centaurea species not previously investigated, C. polyacantha Willd. (sect. Seridia, Asteraceae) and C. maroccana Ball. (sect. Calcitrapa, Asteraceae), collected in Morocco, was evaluated by GC-MS. The main components of the essential oil of the first one were limonene (18.2%), β-bisabolene (11.5%), (Z)-β-farnesene (8.6%), and spathulenol (8.3%), whereas the C. maroccana essential oil, practically devoid of terpenoids, was shown to be rich in some unusual Centaurea metabolites: 1-hexadecanol (24.9%), docosane (23.7%), and 1-octadecanol (19.5%). Furthermore, a complete literature review on the composition of the essential oils of all the other taxa of Centaurea, belonging to sections Seridia and Calcitrapa, studied so far, was performed.

Volatile constituents of the leaf and fruit essential oils of Litsea cubeba (Lour.) Pers. growing wild in Baoshan region, China

The chemical composition of the essential oil from the fruits and leaves of Litsea cubeba (Lour.) Pers. (Lauraceae) growing wild in Baoshan region, Yunnan Province of China was investigated for the first time in 5.36% and 2.16% (w/w) yields, respectively, when analysed by GC and GC/MS. Ten and 25 components were identified in the fruit and leaf oils which constituted 99.15% and 99.4% of the oils. Of the fruit oil, the major components were neral (36.51%), geranial (44.23%), and citronella (8.77%). The major components of the leaf oil were linalool (67.37%), limonene (6.37%), β-bisabolene (6.03%), neral (5.86%), and caryophyllene oxide (3.20%). The analysis of the essential oil obtained from Baoshan revealed a significant abundance of citral and linalool in the fruits and leaves, respectively. This was the first Litsea species to exhibit β-bisabolene as the principal constituent.

Thymus richardii subsp. nitidus (Guss.) Jalas Essential Oil: An Ally against Oral Pathogens and Mouth Health

The genus Thymus L., belonging to the Lamiaceae family, contains about 220 species with a distribution that mainly extends in Europe, northwest Africa, Ethiopia, Asia, and southern Greenland. Due to their excellent biological properties, fresh and/or dried leaves and aerial parts of several Thymus ssp. have been utilized in the traditional medicine of many countries. To evaluate not only the chemical aspects but also the biological properties, the essential oils (EOs), obtained from the pre-flowering and flowering aerial parts of Thymus richardii subsp. nitidus (Guss.) Jalas, endemic to Marettimo Island (Sicily, Italy), were investigated. The chemical composition of the EOs, obtained by classical hydrodistillation and GC-MS and GC-FID analyses, showed the occurrence of similar amounts of monoterpene hydrocarbons, oxygenated monoterpenes, and sesquiterpene hydrocarbons. The main constituents of the pre-flowering oil were β-bisabolene (28.54%), p-cymene (24.45%), and thymol methyl ether (15.90%). The EO obtained from the flowering aerial parts showed as principal metabolites β-bisabolene (17.91%), thymol (16.26%), and limonene (15.59%). The EO of the flowering aerial parts, and its main pure constituents, β-bisabolene, thymol, limonene, p-cymene, and thymol methyl ether were investigated for their antimicrobial activity against oral pathogens and for their antibiofilm and antioxidant properties.

In silico identification of compounds from Nigella sativa seed oil as potential inhibitors of SARS-CoV-2 targets

BACKGROUND

The growing number of cases, severity and fatality of the COVID-19 pandemic, coupled with the fact that no cure has been found has made infected individuals especially in Africa, to resort to the consumption of different natural products to alleviate their condition. One of such plant materials that have been consumed to remedy the severity of this viral infection is the oil of Nigella sativa seed commonly called black seed oil. In this study, we extracted and characterized the oil from this seed using gas chromatography coupled to a mass selective detector to identify the component phytochemicals. Site-directed multiligand docking of the identified compounds was performed on SARS-CoV-2 molecular targets- Replicase polyprotein 1a, RNA binding protein of NSP9, ADP ribose phosphatase of NSP3, 3-chymotrypsin-like protease 3CLpro, and RNA-dependent RNA polymerase RDRP, and ACE2-angiotensin-converting enzyme from the Homo sapiens.

RESULTS

The binding affinity of caryophyllene oxide was the highest on 3CLpro (- 6.0 kcal/mol), NSP3 (- 6.3 kcal/mol), NSP9 (- 6.3 kcal/mol), and RDRP (- 6.9 kcal/mol) targets, while α-bergamotene gave the best binding affinity on RPIA (5.7 kcal/mol) target. The binding affinity of β-bisabolene on the ACE2 target (- 8.0 kcal/mol) was almost the same as Remdesivir (- 8.1 kcal/mol). The ADMET properties of these three phytochemicals showed that they are good drug leads for these SARS-CoV-2 receptors.

CONCLUSION

The findings from this study strongly indicate that the reported recovery from COVID-19 infection claimed by patients who consumed black seed oil could be linked to the presence of caryophyllene oxide, α-bergamotene, and β-bisabolene in this natural product.

The Product Specificities of Maize Terpene Synthases TPS4 and TPS10 Are Determined both by Active Site Amino Acids and Residues Adjacent to the Active Site

Terpene synthases make up a large family of enzymes that convert prenyl diphosphates into an enormous variety of terpene skeletons. Due to their electrophilic reaction mechanism—which involves the formation of carbocations followed by hydride shifts and skeletal rearrangements—terpene synthases often produce complex mixtures of products. In the present study, we investigate amino acids that determine the product specificities of the maize terpene synthases TPS4 and TPS10. The enzymes showed 57% amino acid similarity and produced different mixtures of sesquiterpenes. Sequence comparisons and structure modeling revealed that out of the 43 amino acids forming the active site cavity, 17 differed between TPS4 and TPS10. While combined mutation of these 17 residues in TPS4 resulted in an enzyme with a product specificity similar to TPS10, the additional mutation of two amino acids next to the active site led to a nearly complete conversion of TPS4 into TPS10. These data demonstrate that the different product specificities of TPS4 and TPS10 are determined not only by amino acids forming the active site cavity, but also by neighboring residues that influence the conformation of active site amino acids.

Callicarpa Species from Central Vietnam: Essential Oil Compositions and Mosquito Larvicidal Activities

There are around 140 species in the genus Callicarpa, with 23 species occurring in Vietnam. The Vietnamese Callicarpa species have been poorly studied. In this work, the leaf essential oils of C. bodinieri, C. candicans, C. formosana, C. longifolia, C. nudiflora, C. petelotii, C. rubella, and C. sinuata, have been obtained from plants growing in central Vietnam. The chemical compositions of the essential oils were determined using gas chromatography – mass spectrometry. Mosquito larvicidal activities of the essential oils were carried out against Aedes aegypti. All of the Callicarpa leaf essential oils showed larvicidal activity, but two samples of C. candicans were particularly active with 48-h LC₅₀ values of 2.1 and 3.8 μg/mL. Callicarpacandicans essential oil should be considered as a potential alternative mosquito control agent.

Composition of the essential oil of Stachys benthamiana Boiss. from the south of Iran

The chemical composition of the essential oil (EO) obtained from the aerial parts of Stachys benthamiana Boiss. was analysed by using GC and GC/MS. Thirty-three components were identified in the oil. β-Bisabolene (19.2%), humulene epoxide II (10.7%), epi-α-bisabolol (7.2%), (E)-γ-bisabolene (6.9%), n-decanal (6.8%) and caryophyllene oxide (6.6%), were the main compounds in the EOs. This is the first report on the different chemical compositions of S. benthamiana EOs from the south of Iran.