Infusions of the plant Picrasma excelsa, known as Jamaican bitterwood tea, are commonly consumed to lower blood sugar levels in diabetics who are already on prescription medicines. We therefore investigated the inhibition properties of this tea against a panel of cytochrome P450 (CYP) enzymes, which are primarily responsible for the metabolism of a majority of drugs on the market. The two major ingredients, quassin and neoquassin, were then isolated and used for further characterization. Inhibition of the activities of heterologously expressed CYP microsomes (CYPs 2D6, 3A4, 1A1, 1A2, 2C9, and 2C19) was monitored, and the most potent inhibition was found to be against CYP1A1, with IC (50) values of 9.2 microM and 11.9 microM for quassin and neoquassin, respectively. The moderate inhibition against the CYP1A1 isoform by quassin and neoquassin displayed partial competitive inhibition kinetics, with inhibition constants ( K(i)) of 10.8 +/- 1.6 microM, for quassin and competitive inhibition kinetics, with a K(i) of 11.3 +/- 0.9 microM, for neoquassin. We then docked these two inhibitors into the active site of a model of CYP1A1, which provided insight at the atomic level into the structure-activity relationship of quassinoids with respect to this important CYP isoform known to be an activator of carcinogens, thus providing a useful basis for the search for more potent inhibitors of CYP1A1 that may have implications in chemoprotection.

The results of the reaction of usnic acid (1) with hydroxylamine are presented. Four products, two isomeric isoxazoles (2 and 4), a novel oxazocine structure (3), and Δ2,11-enaminousnic acid (5) were isolated and characterized. These data clarify the earlier published results in this area.

. Can. J. Chem. 55, 2336 (1977). Studies on the biodegradation of (+)-usnic acid (1) by a Pseudomonas species have revealed a novel aromatic deacylation process. The isolated metabolite, (+)-6-desacetylusnic acid (2) is crystalline and its structure is established by means of spectroscopic and chemical methods. The synthesis of 2 from usnic acid (1) is also reported and provides conclusive evidence for the structure of this metabolite.

A study of the fragmentation patterns of the naturally occurring lichen substance, usnic acid (I) and various other chemically and biochemically derived compounds is reported and discussed. From these results it is demonstrated that the characteristic fragmentation patterns observed are of considerable utility in determining not only the substitution patterns on these highly oxygenated molecules, but also the structural elucidation of new compounds within the series.

Pimenta richardii is an endemic flowering plant of Jamaica belonging to the Myrtaceae family. A large number of species within this family remain phytochemically unexplored including Pimenta richardii. Hence, this study determined for the first time the chemical composition and biological activities of P richardii essential oils (EOs) extracted via hydrodistillation at four different times of the year. The EOs’ chemical compositions were analyzed by gas chromatography‐mass spectrometry (GC‐MS) and GC coupled to a flame ionization detector (GC‐FID). A total of 40 compounds were identified in the P richardii EOs by comparison of the Kováts retention indices (RI), mass spectra data with those in the National Institute of Standards and Technology (NIST) library, and co‐elution with authentic samples where available. The main compounds were eucalyptol (56.53%) in April and limonene (40.7%) in July. The in vitro antimicrobial assays were performed using disk diffusion and tube dilution assay to determine the minimum inhibitory concentrations (MICs). P richardii EOs were active against all 10 micro‐organisms used including Klebsiella pneumoniae (ATCC BAA 1705), methicillin‐resistant Staphylococcus aureus—MRSA (63190122), Streptococcus group A (ATCC 19815), and Streptococcus group B (ATCC 12386) having MIC of 0.25, 0.50, 0.06, and 0.06 mg/mL, respectively. Antioxidant activities were evaluated using 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radical scavenging assay. The EOs did not exhibit significant antioxidant property; however, there is potential use of EOs from P richardii in the pharmaceutical industry upon further evaluation.