Trevor Herbert Yee

Inhibition of CYP1A1 by quassinoids found in Picrasma excelsa.

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.

Investigation of Essential Oil Extracts from Four Native Jamaican Species of Bursera for Antibacterial Activity

OBJECTIVE Bacterial infection with organisms resistant to antibiotics have increased during the last few decades worldwide. Because of this increase, the authors decided to subject the essential oils from the stem, leaves and fruits of the four native Jamaica species of Bursera to microbial studies. METHODS Steam distillate extracts from different parts of four native Jamaican spp of Bursera simaruba (Red Birch), Bursera lunanii (Black Birch), Bursera hollickii and Bursera aromatica (Siboney) were tested for their antibacterial activity against six common pathogens: Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Staphylocococcus aureus, methicillin resistant Staphylococcus aureus (MRSA) and beta-haemolytic Streptococcus group A (BHSA) using a disk diffusion assay. RESULTS The investigation revealed that extracts from two of the four plants tested were active against all the pathogens. These were extracts from the fruits and stems of B. simaruba and those from the fruit of B. lunanii. CONCLUSION This study gives credence to the ongoing search for locally available plants whose extracts possess significant antimicrobial activity. This may be useful in the development of naturally derived pharmaceuticals.

The Chemical Composition of the Essential Oils from the Leaves, Bark and Fruits of Bursera simaruba (L.) Sarg. from Jamaica

Abstract Oils of the leaves, bark and fruits of Bursera simaruba collected from the Long Mountain region of Jamaica were isolated by hydrodistillation and analyzed by GC-FID and GC/MS. From our analyses of the oils from the leaves, bark and fruits 46, 54 and 19 components were identified which constituted 93.6%, 97.9% and 100% of the total oils. The leaf oils were dominated by sesquiterpenes (70.1%), the major ones being trans-cadina-1(6),4-diene (9.7%) followed by β-caryophyllene (9.0%), α-humulene (6.2%), β-elemene (5.6%) α-cadinol (4.7%), α-selin-11-en-4-ol (4.2%), caryophyllene oxide (3.2%) and δ-selinene (3.1%). The major monoterpenes were α-pinene (10.2%), myrcene (5.2%) and β-pinene (3.4%). The major monoterpene components of the bark were α-pinene (32.1%), β-pinene (13.5%) and isolimonene (5.6%) while the major sesquiterpenes were viridiflorol (7.1%), β-caryophyllene (4.9%), β-selinene (4.3%), α-humulene (3.1%) and caryophyllene oxide (3.1%). The fruit oil was characterized by a high portion of monoterpenes, the major ones being α-pinene (27.8%), β-pinene (24.1%), terpinen-4-ol (13.3%), sabinene (8.1%), iso-sylvestrene (4.9%), limonene (4.4%) and γ-terpinolene (3.5%).

Chemical Composition and Insecticidal Activity of the Essential Oils from Bursera hollickii (Britton) Found in Jamaica

Abstract The essential oils from the leaves and bark of Bursera hollickii (Britton) collected from Long Mountain, St. Andrew, Jamaica were extracted by hydrodistillation and analyzed by GC and GC/MS. Sixty-two (62) components were identified from the leaf oils which constituted ca. 99% of the oils, while sixty-three (63) components were identified from the bark oils which constituted ca. 97% of the oils. Monoterpenes represented the major components of the oils with α-pinene (49.8% and 34.8%), β-pinene (11.0% and 10.6%), terpinolene (0.7% and 13.4%) and α-terpineol (5.7% and 8.9%) being the major component. Of the sesquiterpenes, the predominant components were β-caryophyllene (4.8% and trace) and α-humulene (3.4% and 0.7%). The oil exhibited toxic action against adult sweet potato weevils, Cylas formicarius elegantulus (Summer), the most destructive pest of sweet potato (Ipomoea batatas). No antioxidant activity was observed for the oils when subjected to the DPPH assay.

The Volatile Constituents From the Leaves, Bark and Fruits of Bursera aromatica (Proctor) Found in Jamaica

Abstract The essential oil from the leaves, bark and fruits of Bursera aromatica (Burseraceae) collected from the Cockpit Country region of Jamaica were obtained by hydrodistillation in 0.03%, 0.09% and 1.12% (w/w) yields, respectively, and were analyzed by GC-FID and GC/MS. Thirty-eight constituents of the leaf oil (92.1%), 26 constituents of the bark oil (96.5%), and 27 constituents of the fruit oil (93.5%) were identified. The predominant compounds were nonane (14.7%, 5.2% and 23.7%), α-copaene (15.8%, 23.7% and 14.0%), β-caryophyllene (21.7%, 12.8% and 6.8%), δ-cadinene (11.3%, 21.5% and 4.3%) and viridiflorol (5.9%, 11.8% and 7.9%) in the oils from the leaves, bark and fruits, respectively. In addition to the components listed above, β-pinene (7.0%) and limonene (8.0%) were also among the major components of the fruit oil.

Chemical Composition of Essential Oils from the Aerial Parts of Jamaican Bursera lunanii Spreng.

Abstract The essential oils from the leaves, bark and fruits of Bursera lunanii from the Long Mountain region of Jamaica were isolated by hydrodistillation and yielded strong odorous, clear yellow oils in 0.19%, 0.16% and 0.19% (w/w) yields, respectively, when analyzed by GC-FID and GC/MS. Forty-two, 48 and 13 components were identified in the leaf, bark and fruit oils which constituted 87.7%, 91.1% and 94% of the oils. The major components of the leaf oil were α-pinene (42.7%), β-caryophyllene (14.2%) and caryophyllene oxide (12.2%). The major components of the bark oil were α-pinene (51.2%) and α-terpineol (6.5%). Of the fruit oil, the major components were verbenone (36.5%), cis-pinanediol (14.7%), trans-verbenol (13.6%), and myrtenal (8.7%).