Activity of methylgerambullin from Glycosmis species (Rutaceae) against Entamoeba histolytica and Giardia duodenalis in vitro

Abstract

Entamoeba histolytica and Giardia duodenalis are widespread intestinal protozoan parasites which both spread via cysts that have to be ingested to infect a new host. Their environment, the small intestine for G. duodenalis and the colon for E. histolytica , contains only very limited amounts of oxygen, so both parasites generate energy by fermentation and substrate level phosphorylation rather than by oxidative phosphorylation. They both contain reducing agents able to reduce and activate nitroimidazole drugs such as metronidazole which is the gold standard drug to treat Entamoeba or Giardia infections. Although metronidazole works well in the majority of cases, it has a number of drawbacks. In animal models, the drug has carcinogenic activity, and concerns about a possible teratogenic activity remain. In addition, the treatment of G. duodenalis infections is hampered by emerging metronidazole resistance. Plant-derived drugs play a dominant role in human medicine, therefore we tested the activity of 14 isolated plant compounds belonging to seven different classes in vitro against both parasites. The tests were performed in a new setting in microtiter plates under anaerobic conditions. The compound with the highest activity was methylgerambullin, a sulphur-containing amide found in Glycosmis species of the family Rutaceae with an EC 50 of 14.5 μM (6.08 μg/ml) after 24 h treatment for E. histolytica and 14.6 μM (6.14 μg/ml) for G. duodenalis . The compound was successfully synthesised in the laboratory which opens the door for the generation of new derivatives with higher activity.

A systematic review of anti-Entamoeba histolytica activity of medicinal plants published in the last 20 years

“…The methanol extract of the stem of Ocimum basilicum (Lamiaceae) with IC 50 value 14.17 μ g mL −1 with active component Caryophyllene, methyl eugeno (Badry et al ., 2010), methanolic extract of root bark and fruit of Syzygium cordatum of myrtaceae with 0.3 μ g mL −1 with active component leucodelphinidin, leucocyanidin (Samie et al ., 2013), the methanolic extract of the whole plant of Pycanthus angolensic (Fabaceae) with IC 50 of 5.3 μ g mL −1 with active component quinines and anthroquinines (Samie et al ., 2013), ethanolic extract of timber of Chlorophora excels of family moraceae 1.95 μ g mL −1 with active component iroko and chlorophorin (Padayachee and Odhav, 2000), acetone extract of Virgillio oroboides of family Fabaceae with IC 50 value 0.25 μ g mL −1 with active component formononetin and maackiain (Padayachee and Odhav, 2000), the ethanolic extract of bark of Terminalia chebula of family Combretaceae with IC 50 value 1.75 μ g mL −1 and active component alagesan (Sohini et al ., 1995) hydroehtanolic extract of the whole family of Tinospora cordifolia of family menispermiaceae 10.4 μ g mL −1 with active component cordifolioside (Sohini et al ., 1995), the dichloromethane extract of the roots of Geranium mexicanum of Germinaceae with IC 50 value of 1.9 μ g mL −1 with active component flavan-3-ol-(-)-epicatechin (Bolanos et al ., 2011). The methanolic extract of the kaempferol of Helianthemum glomeratum (Cistaceae) with IC 50 value 27.7 μ m and active component kaempferol (Bolanos et al ., 2015), the methanol extract of the whole plant of Glycosmis pentaphylla of Rutaceae with an IC 50 value of 14.5 μ g mL −1 and active component methylgerambullin (Drinic et al ., 2019). Butanol and chloroform extract of Piper longum (Piperaceae) with IC50 value in a wide range from 0.0054 μ g mL −1 onwards (Ghoshal et al ., 1996).…”

Comparative phytochemistry of flavaglines (= rocaglamides), a group of highly bioactive flavolignans from Aglaia species (Meliaceae)

“…In continuation of this screening program for antiprotozoal activities aglafoline (4) also showed pronounced activity against Giardia duodenalis trophozoites colonizing the small intestine. The EC 50 values after 24 h and 48 h were 17.2 lmol and 7.71 lmol, respectively (Drinić et al 2019).…”

“…As a consequence, apart from ongoing screenings for insecticidal properties, there has also been a great parallel interest in that class of compounds as potential anticancer agents (Ohse et al 1996;Wu et al 1997;Cui et al 1997;Lee et al 1998;Bohnenstengel et al 1999a,b;Wang and Duh 2001;Hausott et al 2004;Mi et al 2006a;Zhu et al 2007Zhu et al , 2009Cencic et al 2009;Ribeiro et al 2012;Basmadjian et al 2013). Moreover, anti-inflammatory (Baumann et al 2002;Proksch et al 2005;Fahrig et al 2005;Salim et al 2007b), antiprotozoal (Phongmaykin et al 2011;Astelbauer et al 2011Astelbauer et al , 2012Langlais et al 2018;Drinić et al 2019), and more recently, antiviral activities (Biedenkopf et al 2017;Müller et al 2018Müller et al , 2020Müller et al , 2021Todt et al 2018;Glitscher et al 2018;Elgner et al 2018;Henss et al 2018;Schulz et al 2021;Taroncher-Oldenburg et al 2021) were also reported which greatly stimulated further research in this class of compounds.…”

Antimicrobial resistance of the enteric protozoon Giardia duodenalis – A narrative review

“…Also, methylgerambullin, a sulphur-containing amide in Glycosmis spp. (family Rutacea e) [ 131 ], 2,3-Dihydroxyphenyl B-D-glucopyranosiduronic acid as well as the tannins gallic acid and chebulic acid extracted from Terminalia ferdinandiana in combination with ascorbic acid, respectively [ 132 ], and crude Ageratum conyzoides extracts [ 133 ] showed giardicidal effects in vitro and partly also in animal experiments. The giardicidal effects of the latter were associated with changes in the flagella and the ventral discs of G. duodenalis trophozoites [ 133 ].…”