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  1. Permeability of the ellagitannin geraniin and its metabolites in a human colon adenocarcinoma Caco-2 cell culture model
    Elendran S, Muniyandy S, Lee WW, Palanisamy UD
    Food Funct, 2019 Feb 20;10(2):602-615.
    PMID: 30566155 DOI: 10.1039/c8fo01927d
    Ellagitannins, found abundantly in berries, pomegranates, walnuts and almonds, have been increasingly investigated for their health benefits. Geraniin (GE), an ellagitannin, found predominantly in herbal plants, as well has been shown to exhibit a number of biological activities. Like many hydrolysable tannins, geraniin is water-soluble and readily undergoes hydrolysis in the presence of hot water, weak acids and weak bases to yield several metabolites including corilagin (CO), ellagic acid (EA) and gallic acid (GA). There are numerous studies on the pharmacological effectiveness of GE, CO and GA. However, the intestinal permeability of GE and CO has never been investigated before. Caco-2 cell transport assay was utilized to evaluate the in vitro permeability of GE and its metabolites. GE, CO and EA were found to have no apparent permeability (Papp) while GA displayed a Papp value of 31.3 ± 1.1 × 10-6 cm s-1. Mass balance studies showed a loss of geraniin and its metabolites during transport. Chemical stability studies in the transport buffers revealed that GE and CO were hydrolyzed in the HBSS buffers. Experiments using lysed cells revealed that GE and its metabolites were metabolized during transport. Absorption and desorption studies confirmed the accumulation of EA inside the cells. The above results indicate that the compounds have poor oral absorption. To consider these compounds or their natural extracts as oral nutraceutical candidates, formulation strategies are mandatory.
    Matched MeSH terms: Hydrolyzable Tannins/metabolism*
  2. Metabolites of the ellagitannin, geraniin inhibit human ACE; in vitro and in silico evidence
    Looi D, Goh BH, Khan SU, Ahemad N, Palanisamy UD
    Int J Food Sci Nutr, 2021 Jun;72(4):470-477.
    PMID: 33032478 DOI: 10.1080/09637486.2020.1830263
    Hypertension is defined as the persistence of elevated blood pressure in the circulation system. The renin-angiotensin-aldosterone system is a major modulator of blood pressure. Among the risk factors of cardiovascular disease, hypertension is the most preventable and treatable, with drugs such as ACE inhibitors. Many ACE inhibitors are known to have undesirable side effects and hence, natural alternatives are being sought. Dietary polyphenols, particularly ellagitannins, are derived from plant products and are known to exhibit a variety of bioactivities. Geraniin, an ellagitannin has been shown to have antihypertensive activity in animal experiments. It is speculated that the metabolites of geraniin are responsible for its ACE inhibitory activity. We have performed in vitro ACE inhibition and in silico studies with geraniin and its metabolites (ellagic acid, urolithins). Our studies confirm that ellagic acid exhibited similar inhibitory potential to ACE as the positive control captopril.
    Matched MeSH terms: Hydrolyzable Tannins/metabolism*
  3. Fulltext Geraniin extracted from the rind of Nephelium lappaceum binds to dengue virus type-2 envelope protein and inhibits early stage of virus replication
    Abdul Ahmad SA, Palanisamy UD, Tejo BA, Chew MF, Tham HW, Syed Hassan S
    Virol J, 2017 11 21;14(1):229.
    PMID: 29162124 DOI: 10.1186/s12985-017-0895-1
    BACKGROUND: The rapid rise and spread in dengue cases, together with the unavailability of safe vaccines and effective antiviral drugs, warrant the need to discover and develop novel anti-dengue treatments. In this study the antiviral activity of geraniin, extracted from the rind of Nephelium lappaceum, against dengue virus type-2 (DENV-2) was investigated.

    METHODS: Geraniin was prepared from Nephelium lappaceum rind by reverse phase C-18 column chromatography. Cytotoxicity of geraniin towards Vero cells was evaluated using MTT assay while IC50 value was determined by plaque reduction assay. The mode-of-action of geraniin was characterized using the virucidal, attachment, penetration and the time-of-addition assays'. Docking experiments with geraniin molecule and the DENV envelope (E) protein was also performed. Finally, recombinant E Domain III (rE-DIII) protein was produced to physiologically test the binding of geraniin to DENV-2 E-DIII protein, through ELISA competitive binding assay.

    RESULTS: Cytotoxicity assay confirmed that geraniin was not toxic to Vero cells, even at the highest concentration tested. The compound exhibited DENV-2 plaque formation inhibition, with an IC50 of 1.75 μM. We further revealed that geraniin reduced viral infectivity and inhibited DENV-2 from attaching to the cells but had little effect on its penetration. Geraniin was observed to be most effective when added at the early stage of DENV-2 infection. Docking experiments showed that geraniin binds to DENV E protein, specifically at the DIII region, while the ELISA competitive binding assay confirmed geraniin's interaction with rE-DIII with high affinity.

    CONCLUSIONS: Geraniin from the rind of Nephelium lappaceum has antiviral activity against DENV-2. It is postulated that the compound inhibits viral attachment by binding to the E-DIII protein and interferes with the initial cell-virus interaction. Our results demonstrate that geraniin has the potential to be developed into an effective antiviral treatment, particularly for early phase dengue viral infection.

    Matched MeSH terms: Hydrolyzable Tannins/metabolism*
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