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Dr Eduard Mas Claret


Postdoctoral research fellow

Academic and research departments

Department of Chemistry.

My publications

Publications

Mas Claret Eduard, Al Yahyaei Balqees, Chu Shuyu, Elliott Ruan M., Imperato Manuel, Lopez Arnaud, Meira Lisiane B., Howlin Brendan J., Whelligan Daniel K. (2020) An aza-nucleoside, fragment-like inhibitor of the DNA repair enzyme alkyladenine glycosylase (AAG),Bioorganic & Medicinal Chemistry 28 (11) 115507 Elsevier
The DNA repair enzyme AAG has been shown in mice to promote tissue necrosis in response to ischaemic reperfusion or treatment with alkylating agents. A chemical probe inhibitor is required for investigations of the biological mechanism causing this phenomenon and as a lead for drugs that are potentially protective against tissue damage from organ failure and transplantation, and alkylative chemotherapy. Herein, we describe the rationale behind the choice of arylmethylpyrrolidines as appropriate aza-nucleoside mimics for an inhibitor followed by their synthesis and the first use of a microplate-based assay for quantification of their inhibition of AAG. We finally report the discovery of an imidazol-4-ylmethylpyrrolidine as a fragment-sized, weak inhibitor of AAG.
Munissi Joan J.E., Isyaka Sani M., Mas-Claret Eduard, Brabner Molly, Langat Moses K., Nyandoro Stephen S., Mulholland Dulcie A. (2020) Ent-clerodane and ent-trachylobane diterpenoids from Croton dictyophlebodes,Phytochemistry 179 112487 Elsevier
The stem bark and root bark extracts of Croton dictyophlebodes (Euphorbiaceae) yielded seven undescribed ent-clerodanes: 15,16-epoxy-17,12(S)-olide-ent-cleroda-1,3,13(16),14-tetraen-18-oic acid methyl ester (crotodictyo A), 3²,4²:15,16-diepoxy-ent-cleroda-13(16),14-dien-20-al (crotodictyo B), 3²,4²:15,16-diepoxy-ent-cleroda-13(16),14-dien-19,20-dioic acid (crotodictyo C), 3²,4²:15,16-diepoxy-ent-cleroda-13(16),14-dien-20,19-olide (crotodictyo D), 3²,4²:15,16-diepoxy-20,12(R)-olide ent-cleroda-13(16),14-dien-19-oic acid methyl ester (crotodictyo E), 15,16-epoxy-ent-cleroda-3,13(16),14-trien-12-oxo-18-oic acid (crotodictyo F) and 15,16-epoxy-ent-cleroda-1,3,13(16),14-tetraen-12-oxo-18-oic acid (crotodictyo G), in addition to 15,16-epoxy- ent-cleroda-3,13(16),14-trien-12-oxo-18-oic acid methyl ester (crotodictyo H), reported previously as a synthetic derivative, and acetyl aleuritolic acid. The root extract yielded two ent-trachylobanes, ent-trachylobane-18,19-diol, the undescribed ent-trachylobane-2±,19-diol, along with ent-kaur-16-en-19-oic acid and 2-methoxybenzyl benzoate. Compounds were evaluated against the NCI 60 panel of human tumour cell lines at a single dose of 10?5 M, but showed no significant activity.
Isyaka Sani M., Mas-Claret Eduard, Langat Moses K., Hodges Thomas, Selway Bethany, Mbala Blaise M., Mvingu Bienvenu K., Mulholland Dulcie (2020) Cytotoxic diterpenoids from the leaves and stem bark of Croton haumanianus (Euphorbiaceae),Phytochemistry 178 112455 Elsevier
The leaf extract of Croton haumanianus J. Léonard (Euphorbiaceae) yielded twenty-six compounds, including eight previously reported ent-kauranes and an ent-labdane and eight undescribed ent-kauranes, ent-16R-kauran-17-al, ent-3²-hydroxy-16R-kauran-17-al, ent-16S,17-epoxykauran-19-ol, ent-16S,17-epoxykauran-3²-ol, ent-17-palmityloxykaurane-3²,16²-diol, ent-17-palmityloxykauran-16²-ol, ent-3±,18-cyclokaurane-16²,17-diol and 19-nor-16±,17-dihydroxy-ent-kaur-4(18)-ene and three undescribed ent-clerodanes, dimethyl ent-15,16-epoxy-6²-hydroxy-1,3,13(16),14-clerodatetraen-20,12S-olide-18,19-dioate (saniolide A), dimethyl ent-15,16-epoxy-6²-hydroxy-1,3,13(16),14-clerodatetraen-20,12R-olide-18,19-dioate (12-epi-saniolide A), methyl ent-15,16-epoxy-1,3,13(16),14-clerodatetraen-18,6R:20,12S-diolide-19-oate (saniolide B) . The stem bark extract yielded the ent-clerodane crotocorylifuran, and five undescribed ent-isopimaranesent-isopimara-8(14),15-dien-18-al, ent-18-hydroxyisopimara-8(14),15-dien-7-one, ent-isopimara-7,15-dien-18-oic acid, ent-isopimara-7,15-dien-18-ol and ent-isopimara-8,15-dien-7-oxo-18-oic acid. Three compounds, ent-kaurane-3²,16²,17-triol, ent-17-palmityloxykaurane-3²,16²-diol and ent-17-palmityloxykauran-16²-ol, showed selective activity against three of the NCI 60 cancer cell lines, the colon (HCT-116), the melanoma (M14) and the renal (786-0) cancer cell lines at a concentration of 10-5 M.
Whitmore Hannah, Sishtla Kamakshi, Knirsch Walter, Andriantiana Jacky L., Schwikkard Sianne, Mas-Claret Eduard, Nassief Sarah M., Isyaka Sani M., Corson Timothy W., Mulholland Dulcie A. (2020) Bufadienolides and anti-angiogenic homoisoflavonoids from Rhodocodon cryptopodus, Rhodocodon rotundus and Rhodocodon cyathiformis,Fitoterapia 141 104479 Elsevier

Background

Homoisoflavonoids have been shown to have potent anti-proliferative activities in endothelial cells over other cell types and have demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Three species of Rhodocodon (Scilloideaea subfamily of the Asparagaceae family), endemic to Madagascar, R. cryptopodus, R. rotundus and R. cyathiformis, were investigated.

Purpose

To isolate and test homoisoflavonoids for their antiangiogenic activity against human retinal microvascular endothelial cells (HRECs), as well as specificity against other ocular cell lines.

Methods

Plant material was extracted at room temperature with EtOH. Compounds were isolated using flash column chromatography and were identified using NMR and CD spectroscopy and HRESIMS. Compounds were tested for antiproliferative effects on primary human microvascular retinal endothelial cells (HRECs), ARPE19 retinal pigment epithelial cells, 92?1 uveal melanoma cells, and Y79 retinoblastoma cells. HRECs exposed to compounds were also tested for migration and tube formation ability.

Results

Two homoisoflavonoids, 3S-5,7-dihydroxy-(32-hydroxy-42-methoxybenzyl)-4-chromanone (1) and 3S-5,7-dihydroxy-(42-hydroxy-32-methoxybenzyl)-4-chromanone (2), were isolated along with four bufadienolides. Compound 1 was found to be non-specifically antiproliferative, with GI50 values ranging from 0.21?0.85 ¼M across the four cell types, while compound 2 showed at least 100-fold specificity for HRECs over the other tested cell lines. Compound 1, with a 3S configuration, was 700 times more potent that the corresponding 3R enantiomer recently isolated from a Massonia species.

Conclusion

Select homoisoflavonoids have promise as antiangiogenic agents that are not generally cytotoxic.

Waratchareeyakul Watcharee, Fusi Fabio, Durante Miriam, Ahmed Amer, Knirsch Walter, Mas-Claret Eduard, Mulholland Dulcie A. (2020) Vasorelaxing Activity of Stilbenoid and Phenanthrene Derivatives from Brasiliorchis porphyrostele: Involvement of Smooth Muscle CaV1.2 Channels,Planta Medica 86 (09) pp. 631-642 Thieme Gruppe
Five compounds, 3,4?-dihydroxy-3?,5,5?-trimethoxydihydrostilbene, 1, 3,4'-dihydroxy-3',5'-dimethoxydihydrostilbene, 2, 3,4'-dihydroxy-5,5'-dimethoxydihydrostilbene, 3, 9,10-dihydro-2,7-dihydroxy-4,6-dimethoxyphenanthrene, 4, and the previously unreported 1,2,6,7-tetrahydroxy-4-methoxyphenanthrene, 5, were isolated from the South American orchid, Brasiliorchis porphyrostele. An in depth analysis of their vascular effects was performed on in vitro rat aorta rings and tail main artery myocytes. Compounds 1-4 were shown to possess vasorelaxant activity on rings pre-contracted by the ±1 receptor agonist phenylephrine, the CaV1.2 stimulator (S)-(-)-Bay K 8644, or depolarised with high K+ concentrations. However, compound 5 was active solely on rings stimulated by 25 mM but not 60 mM K+. The spasmolytic activity of compounds 1 and 4 was significantly affected by the presence of an intact endothelium. The KATP channel blocker glibenclamide and the KV channel blocker 4-aminopyridine significantly antagonised the vasorelaxant activity of compounds 4 and 1, respectively. In patch-clamp experiments, compounds 1-4 inhibited Ba2+ current through CaV1.2 channels in a concentration-dependent manner, whereas neither compound 4 nor compound 1 affected K+ currents through KATP and KV channels, respectively. The present in vitro, comprehensive study demonstrates that Brasiliorchis porphyrostele may represent a source of vasoactive agents potentially useful for the development of novel antihypertensive agents that has now to be validated in vivo in animal models of hypertension.
Langat Moses K., Ndunda Beth M., Salter Caitlin, Odusina Babatope O., Isyaka Sani M., Mas-Claret Eduard, Onocha Patricia A., Midiwo Jacob O., Nuzillard Jean-Marc, Mulholland Dulcie A. (2020) Diterpenoids from the stem bark of Croton megalocarpoides Friis & M. G. Gilbert,Phytochemistry Letters 39 pp. 1-7 Elsevier
Five previously undescribed compounds, megalocarpoidolide I (1), megalocarpoidolide J (3), 12-epi-crotonzambefuran A (4), megalocarpoidolide K (5), 1-trans-p-hydroxycoumaroyl?geranylgerani-1-ol (6) were isolated from the stem bark of Croton megalocarpoides Friis & M. G. Gilbert. The known ent-trachyloban-18-ol, megalocarpoidolide B, megalocarpoidolide C (2), megalocarpoidolide H, crotocorylifuran, 7,8-dehydrocrotocorylifuran, 1,2-dehydrocrotocorylifuran-2-one, acetyl aleuritolic acid, lupeol, N-trans-p-coumaroyl-32,42-dihydroxyphenylethylamine, dodecyl trans-ferulate and lignoceryl trans-ferulate were also isolated. The structures of the compounds were determined using NMR, IR spectroscopy and HRMS. The structure of compound 1 was determined using Logic for Structural Determination (LSD). Compounds 1, 2 and 3 that were selected for screening based on their ability to add diversity to the NCI small molecule compound collection, were evaluated against the NCI60 panel of human tumour cell lines at 10¼M level but found to be inactive.
Moodley N., Crouch N.R. Crouch, Bastida J., Mas-Claret E., Houghton P., Mulholland D.A. (2020) Organ-specific production of alkaloids from bulbs and seeds of Crinum stuhlmannii subsp. delagoense (Amaryllidaceae),South African Journal of Botany Elsevier
The phytochemistry of both bulbs and seeds of the ethnomedicinal Crinum stuhlmannii subsp. delagoense (Amaryllidaceae) was studied, sourced from a single location simultaneously. Eight alkaloids, including two previously unreported ones, N-methyl-haemanthamide (nivanine), and N-methyl-ent-delagoenine, were isolated along with lycorine, 8,9-methylenedioxophenanthridine, 6-hydroxycrinamine, 6-ethoxycrinamine, haemanthamine and hamayne. Compounds isolated were tested for acetylcholinesterase inhibition.
Takou Dieudonné M., Waffo Alain F. Kamdem, Langat Moses K., Wansi Jean D., Mulcahy-Ryan Lauren E., Schwikkard Sianne L., Opara Elizabeth I., Mas-Claret Eduard, Mulholland Dulcie (2019) Melanin Production Inhibitors from the West African Cassipourea congoensis,Planta Medica International Open 6 (02) pp. e50-e56 Thieme Open
Cassipourea congoensis (syn. Cassipourea malosana) is used in African countries as a skin-lightening agent. Two previously unreported cycloartane triterpenoids, 26-hydroxy-3-keto-24-methy lenecycloartan-30-oic acid 1 and 24-methylene-cycloartan-3²,26,30-triol 2 along with the known mahuannin B 3, 7-methoxymahuannin B 4, 7-methoxygeranin A 5, methyl-3-(4-hydroxy-3-methoxyphenyl)-2E-propenoate, glycerol-1-alkanoate, (E)-3-(4-hydroxy-3-methoxyphenyl)prop-2-enal 6, (-)-syringaresinol 7, and stigmast-5-en-3-O-²-D-glucoside, were isolated from the roots of C. congoensis. The crude extract and compounds 1 and 5 were found to inhibit the production of melanin at 10 ¼M with low cytotoxicity validating the ethno-medicinal use of this plant
Schwikkard Sianne, Whitmore Hannah, Sishtla Kamakshi, Sulaiman Rania S., Shetty Trupti, Basavarajappa Halesha D., Waller Catherine, Alqahtani Alaa, Frankemoelle Lennart, Chapman Andy, Crouch Neil, Wetschnig Wolfgang, Knirsch Walter, Andriantiana Jacky, Mas-Claret Eduard, Langat Moses K., Mulholland Dulcie, Corson Timothy W. (2019) The Antiangiogenic Activity of Naturally Occurring and Synthetic Homoisoflavonoids from the Hyacinthaceae (sensu APGII),Journal of Natural Products American Chemical Society
Excessive blood vessel formation in the eye is implicated in wet age-related macular degeneration, proliferative diabetic retinopathy, neovascular glaucoma, and retinopathy of prematurity, which are major causes of blindness. Small molecule antiangiogenic drugs are strongly needed to supplement existing biologics. Homoisoflavonoids have been previously shown to have potent antiproliferative activities in endothelial cells over other cell types. Moreover, they demonstrated a strong antiangiogenic potential in vitro and in vivo in animal models of ocular neovascularization. Here, we tested the antiangiogenic activity of a group of naturally occurring homoisoflavonoids isolated from the family Hyacinthaceae and related synthetic compounds, chosen for synthesis based on structure?activity relationship observations. Several compounds showed interesting antiproliferative and antiangiogenic activities in vitro on retinal microvascular endothelial cells, a disease-relevant cell type, with the synthetic chromane, 46, showing the best activity (GI50 of 2.3 × 10?4 ¼M).