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Malaysian Journal of Analytical Sciences, Vol. 7, No. 1 (2001) 109-112

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Flavonol glycosides from the leaves of Acacia mangium and related species

Y. Umi Kalsom1, H. I. Khairuddin2 and M. M. Zakri1

1

Department of Biology, Faculty of Science and Environmental Studies, Universiti Putra Malaysia, 43400, Serdang 2 Institute of Biological Sciences, Universiti Malaya, 50603, Kuala Lumpur

(Received 6 September 2000)

Abstract. Several flavonol glycosides have been isolated from the leaves of Acacia mangium, A. auriculiformis, A. richii and A. mangium x A. auriculiformis. A. mangium was characterised by the presence of the 3-glucoside of quercetin, quercetin-3diglucoside in addition to kaempferol-3,7-dirhamnoside and kaempferol-7,4'-digalactoside. On the other hand, A. richii contains myricetin-3-glucoside and kaempferol-3-dixyloside whereas A. auriculiformis contains isorhamnetin and quercetin-7glucoside. These compounds have hitherto never been reported from Acacia.

Abstrak. Beberapa flavonoid glikosida telah diasingkan daripada daun Acacia mangium, A. auriculiformis, A. richii dan A. mangium x A. auriculiformis. A. mangium telah dicirikan dengan kehadiran kuersetin-3-glukosida, kuersetin-3diglukosida dan juga kaemferol-3,7-dirhamnosida dan kaemferol-7,4'-digalaktosida. A. richii sebaliknya mengandungi mirisetin-3-glukosida dan kaemferol-3-dizilosida, manakala A. auriculiformis pula mengandungi isorhamnetin dan kuersetin-7glukosida. Sebatian-sebatian ini belum pernah lagi di laporkan daripada Acacia.

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Key word : Acacia; Leguminosae; leaves; flavonoid glycosides

Introduction Some Acacia species have been investigated for their flavonoids [4, 9] and these have been correlated with systematics and geography. Some triterpenoids, saponin [6, 10], coumarins, tannins, carbohydrates, alkaloids and/or nitrogenous bases [12] and cyanogenic compounds have also been reported [8]. In addition these substances have significant biological activities [12] and might play an important role in the adaptation of plants growing in tropic habitats. The aim of the present work is to analyze and identify the flavonoid glycosides from the leaves of Acacia. Materials and Method

in BAW (n-butanol-acetic acid-water; 4:1:5) and 15%HOAc (15% acetic acid). The aglycones were identified by TLC cochromatography in BAW and HOAc while the sugars were identified by PC cochromatography in BEW (n-butanol-ethanol-water; 4:1:2.2), BAW, PhOH (phenol-water) and TBPW (toluene- n-butanol-pyridine-water; 5:1:3:3). The UV spectral values were in agreement with published results [5]. Two dimensional paper chromatograms of leaf extracts of hybrid, A. auriculiformis x A. mangium was compared with those from A. mangium and A. auriculiformis. Additionally, spots were eluted from 2D-chromatograms on thick paper of hybrid extracts and were then compared with components isolated from the parents. Results and Discussion

Plant material Leaves were analysed from freshly dried plant material collected from Forest Research Institute (FRIM), Kepong. Methods of flavonoid analysis The flavonoids in the leaves of Acacia samples were surveyed by means of 2-dimensional paper chromatography and following standard procedures [3, 5, 7]. In addition to spectral techniques, the flavonoids were identified by PC cochromatography of the glycosides and products of enzyme hydrolyses A total of 17 flavonoid constituents were detected on two dimensional chromatograms. The solvents were n-butanol, glacial acetic acid and water (BAW 4:1:5) and 15% glacial acetic acid (HOAc). In order to identify some of the components found on the 2dimensional chromatograms, the compounds of four samples (fresh plants) were studied in more detail. From these samples 13 compounds were obtained in a more or less pure state by means of preparative layer chromatography. The common aglycones were identified by means of Rf values and colour reaction in UV light when compared with standard markers. In acid-hydrolysed extracts, the flavones were

Y. UMI KALSOM et al.: FLAVONOL GLYCOSIDES FROM THE LEAVES recognized by their distinct dark yellow spots on paper chromatograms in UV light. When fumed with ammonia vapour they became bright yellow. The flavonols appeared yellow in UV light before and after fuming with ammonia. For complete identification of flavonoid glycosides, samples were separated in one-dimensional chromatograms of direct extracts and then pure flavonoid identified using standard methods [3, 5, 7]. These included: complete and mild acid hydrolysis, hydrogen peroxide oxidation, enzymic hydrolysis, cochromatography and UV spectrophotometry. Standard solvents used for chromatography were BAW, PhOH, HOAc and water [7]. Table 1 shows the Rf values, colour reactions and the UV absorption spectra of flavonoids isolated from the leaves of Acacia samples. It was found that the parental components appeared additively in the hybrid (Fig. 1).

Figure 1 : 2D-PC of flavoid spots from the leaf extracts of Acacia species

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Y. UMI KALSOM et al.: FLAVONOL GLYCOSIDES FROM THE LEAVES

Table 1 : Spectral and Rf properties of flavonoids of Acacia mangium and related species _____________________________________________________________________________________________________ Flavonoids detected Source Rfs in UV spectrum in NaOH NaOAc H3BO3 in leaf BAW H2O 15%HOAc PhOH 80%MeOH _____________________________________________________________________________________________________ Myricetin 3-glucoside (1) Ar 74 30 46 38 352, 258 263 374 377 3,7-diglucoside (2) Au, Am, Hy 74 30 47 43 353, 264 269 375 387 Kaempferol 3-dixyloside (7) Ar 7-glucoside (3) Au, Am, Hy 3,7-dirhamnoside (5) Am 7,4'-digalactoside (6) Am 4'-galactoside (8) Hy 3-glucoside (9) Au, Am, Hy 3,7-diglucoside (10) Hy 67 60 78 79 63 83 72 31 40 56 49 66 31 55 44 13 48 48 74 51 65 43 58 59 60 54 66 64 355, 265 347, 270 357, 264 346, 257 375, 265 350, 263 357, 265 272 268 269 270 272 271 271 374 363 371 363 359 360 353 379 365 374 367 (dec.) 373 (dec.) 361 352

Quercetin 3-diglucoside (4) Am 61 68 56 53 355, 287sh., 273 374 377 267 3-glucoside (11) Am 72 28 39 59 354, 258 270 372 375 3'-methyl ether (12) Au 74 72 45 57 345, 268 275 344 373 7-glucoside (13) Au 65 05 10 54 353,280 277 350 375 _____________________________________________________________________________________________________ Am= Acacia mangium; Au = A. auriculiformis; Ar = A. richii; Hy = hybrid A. mangium x A. auriculiformis. BAW = n-BuOH-HOAc-H2O (4:1:5), PhOH = phenol- H2O (3:1); H3BO3 = boric acid; H2O = water; 80%MeOH = 80% methanol; NaOH = naterium hydroxide 15%HOAc = 15% acetic acid; NaOAc = naterium acetate;

In the present study kaempferol, myricetin and quercetin were the only flavonols detected in Acacia samples investigated. This is not unexpected as flavonols were reported to be common constituents of the genus Acacia than the related flavones luteolin and apigenin [4]. Myricetin-3,7-diglucoside, kaempferol-7-glucoside and kaempferol-3-glucoside were detected in all samples except in A. richii which contained myricetin-3-glucoside (figure 2) and kaempferol-3-dixyloside. Kaempferol-3-glucoside was isolated before from the leaves of A. arabica [2]. Quercetin was identified in three samples investigated as its 3-diglucoside, 3-glucoside, 3galactoside, 7-glucoside and 3'-methyl ether (figure 3, isorhamnetin) (after hydrolysis) (Table 1). Quercetin

OH

3' 4'

3-glucoside and quercetin 3-diglucoside was detected in A. mangium whereas isorhamnetin and quercetin-7glucoside was detected in A. auriculiformis. The present discovery of quercetin-3-glucoside, quercetin3-galactoside, quercetin-7-glucoside, isorhamnetin and myricetin-3-glucoside in the samples investigated are also not unexpected since El-Mousallamy and coworkers [1] have already reported the presence of quercetin-3-glucoside and quercetin-3-galactoside in the leaves of A. raddiana. Also, the 3-glucoside, 7glucoside, 3-galactoside of quercetin, myricetin-3glucoside and isorhamnetin were earlier found in the flower of A. latifolia by Voirin and coworkers [11]. Furthermore, quercetin-7-glucoside was a major component whereas isorhamnetin was a minor component in A. latifolia.

OMe

OH

3'

4'

OH

OH

7

O

OH

3 5

HO

7

O

3

O-glucosyl O

5

OH O

OH

OH

Figure 2: M yricetin-3-glucoside

Figure 3: Quercetin-3'-methyl ether

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Y. UMI KALSOM et al.: FLAVONOL GLYCOSIDES FROM THE LEAVES From the point of view of clarifying the chemical background of hybridasation in Acacia (A. mangium x A. auriculiformis), the identification of these various flavonol derivatives confirms the fact that distinctive biochemical processes in flavonoid synthesis are inherited additively from the individual parents. It is clear that A. mangium and A. auriculiformis have the ability to synthesize flavonol and probably also to add glucose to the 3- and 7positions. A. mangium is able to synthesize a 7,4'digalactoside and 3,7-dirhamnoside of kaempferol. By contrast, A. auriculiformis generally lacks these special enzymes, but has the added ability to methylate quercetin in the 3'-position. Acknowledgement This work has been sponsored by IRPA-7 Grant, no. 09-02-04-0097.

References 1. 2. El-Mousallamy, A. M. D., H. H. Barakat, A. M. A.Souleman and S. Awadallah. 1991. Polyphenols of Acacia raddiana. Phytochemistry, 30: 3767-3768. Gupta, S. K. and M. M. Bokadia. 1975. Flavonoids from the flowers of Acacia arabica. Phytochemistry, 28: 1422-1424. Harborne, J. B. 1967. Comparative biochemistry of flavonoids. London: Academic Press. 4. Harborne, J. B. 1971. Chemotaxonomy of the Leguminosae. London: Academic Press. 5. Mabry, T. J. , K. R. Markham and M. B. Thomas. 1970. The systematic identification of Flavonoids. Berlin: Springer-Verlag. 6. Mahato, S. B., B. C. Pal and A. K. Nandy 1992. Structure elucidation of two acylated triterpenoid bisglycosides from Acacia auriculiformis Cunn. Tetrahedron, 48: 6717-6128. 7. Markham, K. R. 1982. Techniques of flavonoid identification. London: Academic Press. 8. Seiger, E. E., D. S. Maslin and B. R. Dunn 1989. Cynogenesis in Acacia subgenus aculeiferum. Phytochemistry, 28: 817-820. 9. Tindale, M. and Roux, D. G. 1975. Phytochemical studies in the heart-woods and barks of Australia species of Acacia. Boissiera. 24: 299-305. 10. Uniyal, S. K., V. Badoni, and O. P. Sati 1992. A new triterpenoid saponin from Acacia auriculiformis. J. Nat. Prod. 55: 500-502. 11. Voirin, B., C. Bayet, J. F. Bonvin and A. G. Nair 1986. Flavonoids from the flowers of Acacia latifolia. J. Nat. Prod., 49: 943. 12. Wassel, G. M., S. M. Abd. El-Wahab, N. M. Ammar and M. S. Afifi 1992. Phytochemical examination and biological studies of Acacia nilotica L. Willd and Acacia farnesiana L. Willd growing in Egypt. Egypt. J. Pharm. Sci. 33: 327-340. 3.

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