Phytochemical Characterization of Xerospermum Noronhianum
Xerospermum noronhianum, locally known as gigi buntal (globe-fish’s teeth) or rambutan pachat (leech’s rambutan) is a species belonging to the Sapindaceae family. The Sapindaceae are generally well known as a prolific source of plant saponins. However, to date, there has been no systematic phytoc...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2008
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| Online Access: | http://psasir.upm.edu.my/id/eprint/7167/1/IB_2008_9a.pdf http://psasir.upm.edu.my/id/eprint/7167/ |
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| Summary: | Xerospermum noronhianum, locally known as gigi buntal (globe-fish’s teeth) or
rambutan pachat (leech’s rambutan) is a species belonging to the Sapindaceae family.
The Sapindaceae are generally well known as a prolific source of plant saponins.
However, to date, there has been no systematic phytochemical and biological evaluation
on this particular species. In the present study, several known compounds have been
successfully isolated from various plant parts and solvent fractions of Xerospermum
noronhianum. Three new triterpenoid saponins have been purified from the ethyl acetate
and aqueous fractions of both stem and leaf of the plant. Through the use of high field
NMR and mass spectroscopy, these saponins have been identified to be those of the
oleanane-type, i.e 3-O-{α-L-rhamnopyranosyl(1→2)-β-D-fucopyranosyl}-28-O-{[α-Lrhamnopyranosyl(
1→2)][α-L-rhamnopyranosyl(1→6)]}-β-D-glucopyranosyl oleanolic
acid, 3-O-{α-L-rhamnopyranosyl(1→3)-β-D-fucopyranosyl}-28-O-{α-Lrhamnopyranosyl(
1→4)}-β-D-glucopyranosyl oleanolic acid and 3-O-{α-Lrhamnopyranosyl(
1→2)-[3’,4’-diacetoxy-β-D-fucopyranosyl]}-28-O-{α-L rhamnopyranosyl(1→2)}-β-D-glucopyranosyl oleanolic acid. Several known compounds
have also been isolated and identified as the free triterpenes namely lupeol, oleanolic
acid, friedelin, 3β-hydroxy-29-nor-20-lupenone, 3β-hydroxy-lup-20(29)en-30-al,
mixture of 3β-hydroxyolean-12-en-11-one and 3β-hydroxyurs-12-en-11-one; the
flavonoid glycosides kampferol-3-O-rhamnoside, quercetin-3-O-rhamnoside; the
benzoic acid derivatives 3,5-dihydroxy-4-methoxybenzoic acid, 3,4-dihydroxybenzoic
acid, 3,4,5-trihydroxybenzoic acid; as well as scopoletin, lupeol palmitate, and palmitic
acid, mixture of β-sitosterol and stigmasterol and mixture of their glycosides. Oxidation
of the major compound, lupeol, successfully yielded lupenone as the product.
The crude extracts and isolated pure compounds were also further evaluated for their
anti-cholinesterase activity, against two enzymes; acetylcholinesterase and
butyrylcholinesterase, using thin layer chromatography bioautographic method. The
inhibition activities of the test samples were expressed as pMIQ values, which represents
the negative logarithm of the minimal inhibitory quantity (in moles) that produced the
spot with the least observable whiteness. Generally, the crude extracts of stem, leaf and
bark parts, all showed inhibition in the preliminary screening by giving white observable
inhibition spots against a yellow-coloured background. The enzyme inhibiting
constituents were, in part, found to be due to the triterpenoidal saponins, the free
triterpenes as well as the sterol and its glycosides. However, the tested compounds were
considered to be weakly active due to their low pMIQ values. Compounds with pMIQ
values ≥ 10.5 is considered to be bioactive. All of the tested compounds in this study
gave pMIQ value in the range of 1.7 to 3.7. |
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