Browsing by Author "Langat, Moses K."

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    Antiangiogenic Activity and Cytotoxicity of Triterpenoids and Homoisoflavonoids from Massonia pustulata and Massonia bifolia
    (Thieme, 2018-07) Schwikkard, Sianne L.; Whitmore, Hannah; Corson, Timothy W.; Sishtla, Kamakshi; Langat, Moses K.; Carew, Mark; Mulholland, Dulcie A.; Ophthalmology, School of Medicine
    The Hyacinthaceae family (sensu APGII), with approximately 900 species in around 70 genera, plays a significant role in traditional medicine in Africa as well as across Europe and the Middle and Far East. The dichloromethane extract of the bulbs of Massonia pustulata (Hyacinthaceae sensu APGII) yielded two known homoisoflavonoids, (R)-5-hydroxy-3-(4-hydroxybenzyl)-7-methoxy-4-chromanone 1 and 5-hydroxy-3-(4-hydroxybenzyl)-7-methoxy-4-chromone 2 and four spirocyclic nortriterpenoids, eucosterol 3, 28-hydroxyeucosterol 4 and two previously unreported triterpenoid derivatives, (17S,23S)-17α,23-epoxy-3β,22β,29-trihydroxylanost-8-en-27,23-olide 5, and (17S, 23S)-17α,23-epoxy-28,29-dihydroxylanost-8-en-3-on-27,23-olide 6. Compounds 1, 2, 3, and 5 were assessed for cytotoxicity against CaCo-2 cells using a neutral red uptake assay. Compounds 1, 2, and 5 reduced cell viability by 70% at concentrations of 30, 100, and 100 µM, respectively. Massonia bifolia yielded three known homoisoflavonoids, (R)-(4′-hydroxy)-5-hydroxy-7-methoxy-4-chromanone 1, (R)-(4′-hydroxy)-5,7-dihydroxy-4-chromanone 7 and (R)-(3′-hydroxy-4′-methoxy)-5,7-dihydroxy-4-chromanone 9, two previously unreported homoisoflavonoids, (E)-3-benzylidene-(3′,4′-dihydroxy)-5-hydroxy-7-methoxy-4-chromanone 8 and (R)-(3′,4′-dihydroxy)-5-hydroxy-7-methoxy-4-chromanone 10, and a spirocyclic nortriterpenoid, 15-deoxoeucosterol 11. Compounds 1, 1Ac, 7, 8, 9, and 10 were screened for antiangiogenic activity against human retinal microvascular endothelial cells. Some compounds showed dose-dependent antiproliferative activity and blocked endothelial tube formation, suggestive of antiangiogenic activity.
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    The Antiangiogenic Activity of Naturally-occurring and synthetic Homoisoflavonoids from the Hyacinthaceae (sensu APGII)
    (American Chemical Society, 2019-04-05) 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.; Ophthalmology, School of Medicine
    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 μM).