Bhuwan K. Chhetri

Scalable, Metal- and Additive-Free, Photoinduced Borylation of Haloarenes and Quaternary Arylammonium Salts.

We report herein a simple, metal- and additive-free, photoinduced borylation of haloarenes, including electron-rich fluoroarenes, as well as arylammonium salts directly to boronic acids. This borylation method has a broad scope and functional group tolerance. We show that it can be further extended to boronic esters and carried out on gram scale as well as under flow conditions.

Additive- and Metal-Free, Predictably 1,2- and 1,3-Regioselective, Photoinduced Dual C–H/C–X Borylation of Haloarenes

We report herein a simple, additive- and metal-free, photoinduced, dual C-H/C-X borylation of chloro-, bromo-, and iodoarenes. The reaction produces 1,2- and 1,3-diborylarenes on gram scales under batch and continuous flow conditions. The regioselectivity of the dual C-H/C-X borylation is determined by the solvent and the substituents in the parent haloarenes.

A Survey of Chemical Compositions and Biological Activities of Yemeni Aromatic Medicinal Plants

Yemen is a small country located in the southwestern part of the Arabian Peninsula. Yemen’s coastal lowlands, eastern plateau, and deserts give it a diverse topography, which along with climatic factors make it opulent in flora. Despite the introduction of Western medicinal system during the middle of the twentieth century, herbal medicine still plays an important role in Yemen. In this review, we present a survey of several aromatic plants used in traditional medicine in Yemen, their traditional uses, their volatile chemical compositions, and their biological activities.

Bioactivities and Compositions of Betula nigra Essential Oils

The essential oils of Betula nigra (river birch, Betulaceae) buds, leaves, and inner bark were extracted by hydrodistillation and analyzed by GCMS. The bud essential oils were dominated by eugenol and paraffin hydrocarbons, the leaf oils were rich in (2E)-hexenal, linalool, and eugenol, and the bark essential oils were composed largely of fatty acids, paraffin hydrocarbons, and benzenoid aromatics. A screening of the oils for biological activity, including phytotoxic activity against Lactuca sativa (lettuce) and Lolium perenne (perennial ryegrass), nematocical activity against Caenorhabditis elegans, brine shrimp lethality against Artemia salina, insecticidal activity using Solenopsis invicta × richteri (red imported fire ant), and antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. The leaf oil demonstrated notable biological activity in all bioassays. INTRODUCTION Birch preparations, such as teas and infusions, have been important as traditional medicines in several cultures worldwide. The oil from B. alba bark (birch tar) has been used to preserve leather in northern Europe and has demonstrated insect repellent activity, while a tea prepared from B. alba leaves has been used for treatment of gout, rheumatism, and dropsy (Grieve, 1971). In Ayurveda, the essential oil of B. alba is used in treating eczema and psoriasis and to combat hair loss (Vinod et al., 2012). A decoction of the inner bark of B. occidentalis was used by western Native Americans to treat colds, coughs, and other pulmonary ailments (Lewis and ElvinLewis, 1977). The Makandwewininiwag band of the Ojibwe people used a tea prepared from B. pumila buds as a postparturition tonic, while B. pumila buds were heated to make an incense to treat respiratory disorders (Lewis and Elvin-Lewis, 1977). Teas made from the bark of B. lenta were used by Native Americans to treat stomachaches and lung ailments, and teas made from bark and from twigs were used for treating fevers. The essential oil from B. lenta has been used for treatment of rheumatism, gout, scrofula, bladder infections, and neuralgia, and also as an anti-inflammatory analgesic (Foster and Duke, 1990). Betula nigra L., river birch, is a tree native to the southeastern United States (Grelen, 1990). This woody plant, which has reddish-brown shredding bark and simple, alternate, double-toothed leaves, and which can grow over 20 m in height, was used by Southeastern Native Americans in traditional medicines. The Catawba people boiled B. nigra buds to make syrup that was mixed with sulfur for treatment of ringworm and sores (Speck, 1944). The Cherokee chewed leaves to treat dysentery and used a tea made from the bark to treat colds, stomachaches, and urination difficulties (Casey and Wynia, 2010). Creek Indians used B. nigra to treat tuberculosis (Hutton, 2010). European-Americans that settled in the Ozark and Ouachita Mountains discovered B. nigra was useful in treating wounds and urinary pains (Nolan, 1998). Woods et al.: Bioactivities and Compositions of Betula nigra Essential Oils

Antimicrobial, Antioxidant, and Cytotoxic Activities of Ocimum forskolei and Teucrium yemense (Lamiaceae) Essential Oils

Background: Ocimum forskolei and Teucrium yemense (Lamiaceae) are used in traditional medicine in Yemen. Methods: The chemical composition, antimicrobial, antioxidant and cytotoxic activities of the essential oils isolated from the leaves of Ocimum forskolei Benth. (EOOF) and two different populations of Teucrium yemense Deflers., one collected from Dhamar province (EOTY-d), and another collected from Taiz (EOTY-t) were investigated. The antimicrobial activities of the oils were evaluated against several microorganisms with the disc diffusion test or the broth microdilution test. The essential oils were screened for in-vitro cytotoxic activity against human tumor cells. EOOF and EOTY-d were screened for free-radical-inhibitory activity using the DPPH radical scavenging assay. Results: Sixty-four compounds were identified in (EOOF) representing 100% of the oil content with endo-fenchol (31.1%), fenchone (12.2%), τ-cadinol (12.2%), and methyl (E)-cinnamate (5.1%) as the major compounds. In EOTY-d, 67 compounds were identified, which made up 91% of the total oil. The most abundant constituents were (E)-caryophyllene (11.2%), α-humulene (4.0.%), γ-selinene (5.5%), 7-epi-α-selinene (20.1%), and caryophyllene oxide (20.1%), while the major compounds in EOTY-t were α-pinene (6.6%), (E)-caryophyllene (19.1%) α-humulene (6.4%), δ-cadinene (6.5%), caryophyllene oxide (4.3%), α-cadinol (9.5%), and shyobunol (4.6%). The most sensitive microorganisms for EOOF were B. subtilis, S. aureus, and C. albicans with inhibition zones of 34, 16, and 24 mm and MIC values of, 4.3 mg/mL, 4.3 mg/mL, and 8.6 mg/mL, respectively. EOTY-t showed antimicrobial activity against S. aureus, B. cereus, A. niger, and B. cinerea with MIC values of 0.156, 0.156, 0.313 and 0.313 mg/mL, respectively. Neither essential oil showed remarkable radical inhibition (IC50 = 31.55 and 31.41 μL/mL). EOTY-d was active against HT-29 human colorectal adenocarcinoma cell lines with IC50 = 43.7 μg/mL. Consistent with this, EOTY-t was active against both MCF-7 and MDA-MB-231 human breast adenocarcinoma cells. Conclusions: The antimicrobial activity of Ocimum forskolei essential oil against B. subtilis and C. albicans is consistent with its traditional use in Yemeni traditional medicine to treat skin infections. Both O. forskolei and T. yemense show wide variations in their respective essential oil compositions; there remains a need to investigate both species botanically, genetically, and phytochemically more comprehensively.