Natural Product Research Formerly Natural Product Letters
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
A new acylated flavonol from the aerial parts of Asteriscus maritimus (L.) Less (Asteraceae) Marwa I. Ezzat, Shahira M. Ezzat, Kadriya S. El Deeb, Ahlam M. El Fishawy & Sayed A. El-Toumy To cite this article: Marwa I. Ezzat, Shahira M. Ezzat, Kadriya S. El Deeb, Ahlam M. El Fishawy & Sayed A. El-Toumy (2016): A new acylated flavonol from the aerial parts of Asteriscus maritimus (L.) Less (Asteraceae), Natural Product Research, DOI: 10.1080/14786419.2016.1138298 To link to this article: http://dx.doi.org/10.1080/14786419.2016.1138298
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Date: 04 February 2016, At: 03:19
Natural Product Research, 2016 http://dx.doi.org/10.1080/14786419.2016.1138298
A new acylated flavonol from the aerial parts of Asteriscus maritimus (L.) Less (Asteraceae) Marwa I. Ezzata, Shahira M. Ezzata, Kadriya S. El Deeba, Ahlam M. El Fishawya and Sayed A. El-Toumyb Faculty of Pharmacy, Pharmacognosy Department, Cairo University, Cairo, Egypt; bChemistry of Tannins Department, National Research Centre, Cairo, Egypt
Downloaded by [La Trobe University] at 03:19 04 February 2016
a
ABSTRACT
Phytochemical investigation of the flowering aerial parts of Asteriscus maritimus (L.) Less (Asteraceae) led to the isolation of a new compound: patuletin 7-O-β-D-[(2″′S) 6″(3″′-hydroxy-2″′-methylpropanoyl)] glucopyranoside, together with five known metabolites; β-sitosterol 2, chlorogenic acid 3, P-hydroxy -methylbenzoate 4, luteolin 5 and protocatechuic acid 6. The structures of the isolated compounds were determined by comprehensive analyses of its 1D and 2D NMR, HRMS and compared with previously known analogues. The ethanolic extract of the flowering aerial parts of A. maritimus was found to be safe (LD50 = 4.6 mg/kg) and possess significant antioxidant and anti-inflammatory activities and this was in accordance with its high phenolic content (107.36 ± 0.051 mg GAE/g extract).
ARTICLE HISTORY
Received 16 February 2015 Accepted 14 December 2015 KEYWORDS
Asteriscus maritimus; acylated flavonol; antioxidant; antiinflammatory
1. Introduction Over the past 20 years, considerable attention has been given to Asteriscus genus in which mainly sesquiterpenes, as asteriscunolides and aquatolide were isolated (San Feliciano CONTACT Marwa I. Ezzat [email protected] Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/14786419.2016.1138298. © 2016 Taylor & Francis
Downloaded by [La Trobe University] at 03:19 04 February 2016
2
M. I. Ezzat et al.
al. 1984, 1989; El-Dahmy et al. 1985; Jakupovic et al. 1987; Rauter et al. 2001). Previous phytochemical analysis of certain Asteriscus species led to the isolation of flavonoids (Ahmed et al. 1991; Youssef et al. 1995), bisabolone hydroperoxides (Sarg et al. 1994), farnesol and thymol derivatives (Ahmed 1992). Sulphur-containing metabolites, asterisulphoxide, and asterisulphone were isolated from the root of A. maritimus (Medimagh-Saidana et al. 2014). Few studies focused their attention on the composition of the oil prepared from other species (Aboutabl & Hammerschmid 1989; Znini et al. 2011), while the essential oil of A. maritimus was investigated (Fraternale et al. 2001). It was found that other Asteriscus species possess a wide spectrum of biological activities, such as, molluscicidal cercaricidal (Shabana et al. 1988), antimicrobial (Zaki et al. 1984; Sarg et al. 1994) and insecticidal (Pascual-Villalobos and Robledo 1999; Fraternale et al. 2001) activities. The present study deals with the isolation and identification of a new acylated flavonol in addition to five known compounds that were isolated for the first time from the aerial part. Also, the acute toxicity, antioxidant and anti-inflammatory effects of the ethanolic extract were investigated.
2. Results and discussion Phytochemical investigation of the flowering aerial parts of A. maritimus afforded a new flavonoid 1 in addition to five known metabolites (Figure 1). The structures of the known compounds were established by comparing their UV, 1H and 13C NMR spectroscopic data with those in the literature review and confirmed through co-chromatography with authentic samples. They were identified as β-sitosterol 2 (Goad & Akihisa 1997), chlorogenic acid 3 (Sook et al. 2010), P-hydroxy-methylbenzoate 4 (Pouchert 1993; Pouchert & Behnke 1993), luteolin 5 (Mabry et al. 1970) and protocatechuic acid 6 (Lee et al. 2010). Compound 1 was obtained as a yellow microcrystalline powder showing chromatographic properties (yellow spot under UV light). The UV spectrum in MeOH exhibited characteristic absorbance bands of flavonol at 258 and 371 nm. The band at 371 nm was shifted + 58 nm by AlCl3/HCl and + 18 nm by NaOAc/H3BO3. These results suggested that compound 1 was a flavonol with a hydroxyl group at C-5 and an ortho-dihydroxyl group in the B ring (Mabry et al. 1970; Harborne et al. 1975). Its molecular formula was established as C26H27O15 from its HRESI-MS at m/z 579.1346. The 1H NMR spectrum of 1 (DMSO-d6) showed aromatic signals at δ 7.73 (d, J = 2.1, H-2′), 7.53 (dd, J = 8.4, 2.1 Hz, H-6′), 6.9 (d, J = 8.4 Hz, H-5′) and 6.89 (s, H-8). Also, 1 H NMR showed one signal anomeric proten, a hexose anomeric proton resonance at δ 5.17 (d, J = 8 Hz, H-1″) indicating the presence of sugar with β-configuration. The β-D-configuration 13 was deduced from specific optical rotation [𝛼]20 D + 69.4º. C DEPT experiments showed 2 methyl groups, 2 methylene group, 10 methine and 12 quaternary carbons together with molecular formula C26H27O15. Accordingly, the 1H NMR spectrum of 1 displayed signals for one secondary methyl at δ 0.94 (d, J = 6 Hz, H-4″′), one methine at δ 2.48 (m, H-2″′) and one oxygenated methylene at δ 3.41 (d, J = 6.3 Hz, H-3″′a,b). These data were in accordance with published values for 3-hydroxy-2-methylpropanoyl esters (Materska et al. 2003). The 13C NMR spectrum showed two singlets at δ 176.68 and 174.70 assigned to the carbonyls carbons. A comparison of 13C NMR spectra with the literature review data (Roitman & James 1985) points to its great similarity to patuletin 7-O-β-glucopyranoside. However, there were some differences in compound 1 additional resonance was found in 13C NMR spectrum that pointed to the presence of four carbon atoms and a 1H NMR analysis confirmed of a 2-methyl-3-hydroxyl propanoyl substituent. A downfield shift at C-6″ (δ 63.90) of the glucopyranosyl residue in the 13C NMR
Natural Product Research
3
4''' 3''' 2'''
OH
OH
O O
5''
4''
HO
2'
HO
O
H
6''
H
OH
3'
1'''
3''
H
O 1''
2''
OH
O
7
H
9
1'
5'
2 6'
10 6
H3CO
H
1
8
4'
3 4
5
OH
OH
O
1
Downloaded by [La Trobe University] at 03:19 04 February 2016
O HO
OH
O OH
O HO HO
HO
2
3
OH OH
O
OCH3
OH
O OH
O
HO
HO OH
4
OH
O
5
OH
6
Figure 1. Chemical structure of the compounds isolated from A. maritimus.
spectrum proved that this substituent was located at C-6 (Charia et al. 1977). The application of HMQC and HMBC experiments led to full assignments of the 1H and 13C NMR chemical shifts of compound 1. HSQC experiments which correlated all proton resonances with those of each corresponding carbon. In the HMBC spectrum, the pattern of 1H–13C correlation was observed between δ H 5.17 (H-1″) with δ C 156.6 (C-7) indicating a glucosyl moiety is attached to C-7. The HMBC and HSQC data confirmed the location of the propinyl unit at C-6″ through the observed correlations among H-6″ (δ 3.96, 4.44) and C-1″′ (δ 174.7). The substitution at C-2″′ by methyl and methine groups was confirmed by the long-range correlations between the protons of these groups and carbonyl group (δ 174.7). The positive cotton effect observable in the circular dichroism (CD) spectrum indicated that the absolute configuration at the 2″′-position of compound 1 was S. Based on the above data, compound 1 is deduced to be patuletin 7-O-β-D-[(2″′S) 6″(3″′-hydroxy-2″′-methyl-propanoyl)] glucopyranoside.
4
M. I. Ezzat et al.
Table 1. Acute anti-inflammatory activity of the ethanol extract of the flowering aerial parts of A. maritimus (L.) Less. % Oedema Group (n = 6) Control The ethanolic extract of A. maritimus Indomethacin
Dose mg/kg b.wt. 1 mL saline 100 20
Mean ± S.E. 59.4 ± 1.6 36.8 ± 1.3* 22.6 ± 0.4*
% of Change – 38 62
Potencya – 0.61 1
Downloaded by [La Trobe University] at 03:19 04 February 2016
Note: % of change calculated as regard the control group. a Potency calculated as compared to the standard anti-inflammatory drug Indomethacin. * p
ISSN: 1478-6419 (Print) 1478-6427 (Online) Journal homepage: http://www.tandfonline.com/loi/gnpl20
A new acylated flavonol from the aerial parts of Asteriscus maritimus (L.) Less (Asteraceae) Marwa I. Ezzat, Shahira M. Ezzat, Kadriya S. El Deeb, Ahlam M. El Fishawy & Sayed A. El-Toumy To cite this article: Marwa I. Ezzat, Shahira M. Ezzat, Kadriya S. El Deeb, Ahlam M. El Fishawy & Sayed A. El-Toumy (2016): A new acylated flavonol from the aerial parts of Asteriscus maritimus (L.) Less (Asteraceae), Natural Product Research, DOI: 10.1080/14786419.2016.1138298 To link to this article: http://dx.doi.org/10.1080/14786419.2016.1138298
View supplementary material
Published online: 01 Feb 2016.
Submit your article to this journal
Article views: 4
View related articles
View Crossmark data
Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=gnpl20 Download by: [La Trobe University]
Date: 04 February 2016, At: 03:19
Natural Product Research, 2016 http://dx.doi.org/10.1080/14786419.2016.1138298
A new acylated flavonol from the aerial parts of Asteriscus maritimus (L.) Less (Asteraceae) Marwa I. Ezzata, Shahira M. Ezzata, Kadriya S. El Deeba, Ahlam M. El Fishawya and Sayed A. El-Toumyb Faculty of Pharmacy, Pharmacognosy Department, Cairo University, Cairo, Egypt; bChemistry of Tannins Department, National Research Centre, Cairo, Egypt
Downloaded by [La Trobe University] at 03:19 04 February 2016
a
ABSTRACT
Phytochemical investigation of the flowering aerial parts of Asteriscus maritimus (L.) Less (Asteraceae) led to the isolation of a new compound: patuletin 7-O-β-D-[(2″′S) 6″(3″′-hydroxy-2″′-methylpropanoyl)] glucopyranoside, together with five known metabolites; β-sitosterol 2, chlorogenic acid 3, P-hydroxy -methylbenzoate 4, luteolin 5 and protocatechuic acid 6. The structures of the isolated compounds were determined by comprehensive analyses of its 1D and 2D NMR, HRMS and compared with previously known analogues. The ethanolic extract of the flowering aerial parts of A. maritimus was found to be safe (LD50 = 4.6 mg/kg) and possess significant antioxidant and anti-inflammatory activities and this was in accordance with its high phenolic content (107.36 ± 0.051 mg GAE/g extract).
ARTICLE HISTORY
Received 16 February 2015 Accepted 14 December 2015 KEYWORDS
Asteriscus maritimus; acylated flavonol; antioxidant; antiinflammatory
1. Introduction Over the past 20 years, considerable attention has been given to Asteriscus genus in which mainly sesquiterpenes, as asteriscunolides and aquatolide were isolated (San Feliciano CONTACT Marwa I. Ezzat [email protected] Supplemental data for this article can be accessed at http://dx.doi.org/10.1080/14786419.2016.1138298. © 2016 Taylor & Francis
Downloaded by [La Trobe University] at 03:19 04 February 2016
2
M. I. Ezzat et al.
al. 1984, 1989; El-Dahmy et al. 1985; Jakupovic et al. 1987; Rauter et al. 2001). Previous phytochemical analysis of certain Asteriscus species led to the isolation of flavonoids (Ahmed et al. 1991; Youssef et al. 1995), bisabolone hydroperoxides (Sarg et al. 1994), farnesol and thymol derivatives (Ahmed 1992). Sulphur-containing metabolites, asterisulphoxide, and asterisulphone were isolated from the root of A. maritimus (Medimagh-Saidana et al. 2014). Few studies focused their attention on the composition of the oil prepared from other species (Aboutabl & Hammerschmid 1989; Znini et al. 2011), while the essential oil of A. maritimus was investigated (Fraternale et al. 2001). It was found that other Asteriscus species possess a wide spectrum of biological activities, such as, molluscicidal cercaricidal (Shabana et al. 1988), antimicrobial (Zaki et al. 1984; Sarg et al. 1994) and insecticidal (Pascual-Villalobos and Robledo 1999; Fraternale et al. 2001) activities. The present study deals with the isolation and identification of a new acylated flavonol in addition to five known compounds that were isolated for the first time from the aerial part. Also, the acute toxicity, antioxidant and anti-inflammatory effects of the ethanolic extract were investigated.
2. Results and discussion Phytochemical investigation of the flowering aerial parts of A. maritimus afforded a new flavonoid 1 in addition to five known metabolites (Figure 1). The structures of the known compounds were established by comparing their UV, 1H and 13C NMR spectroscopic data with those in the literature review and confirmed through co-chromatography with authentic samples. They were identified as β-sitosterol 2 (Goad & Akihisa 1997), chlorogenic acid 3 (Sook et al. 2010), P-hydroxy-methylbenzoate 4 (Pouchert 1993; Pouchert & Behnke 1993), luteolin 5 (Mabry et al. 1970) and protocatechuic acid 6 (Lee et al. 2010). Compound 1 was obtained as a yellow microcrystalline powder showing chromatographic properties (yellow spot under UV light). The UV spectrum in MeOH exhibited characteristic absorbance bands of flavonol at 258 and 371 nm. The band at 371 nm was shifted + 58 nm by AlCl3/HCl and + 18 nm by NaOAc/H3BO3. These results suggested that compound 1 was a flavonol with a hydroxyl group at C-5 and an ortho-dihydroxyl group in the B ring (Mabry et al. 1970; Harborne et al. 1975). Its molecular formula was established as C26H27O15 from its HRESI-MS at m/z 579.1346. The 1H NMR spectrum of 1 (DMSO-d6) showed aromatic signals at δ 7.73 (d, J = 2.1, H-2′), 7.53 (dd, J = 8.4, 2.1 Hz, H-6′), 6.9 (d, J = 8.4 Hz, H-5′) and 6.89 (s, H-8). Also, 1 H NMR showed one signal anomeric proten, a hexose anomeric proton resonance at δ 5.17 (d, J = 8 Hz, H-1″) indicating the presence of sugar with β-configuration. The β-D-configuration 13 was deduced from specific optical rotation [𝛼]20 D + 69.4º. C DEPT experiments showed 2 methyl groups, 2 methylene group, 10 methine and 12 quaternary carbons together with molecular formula C26H27O15. Accordingly, the 1H NMR spectrum of 1 displayed signals for one secondary methyl at δ 0.94 (d, J = 6 Hz, H-4″′), one methine at δ 2.48 (m, H-2″′) and one oxygenated methylene at δ 3.41 (d, J = 6.3 Hz, H-3″′a,b). These data were in accordance with published values for 3-hydroxy-2-methylpropanoyl esters (Materska et al. 2003). The 13C NMR spectrum showed two singlets at δ 176.68 and 174.70 assigned to the carbonyls carbons. A comparison of 13C NMR spectra with the literature review data (Roitman & James 1985) points to its great similarity to patuletin 7-O-β-glucopyranoside. However, there were some differences in compound 1 additional resonance was found in 13C NMR spectrum that pointed to the presence of four carbon atoms and a 1H NMR analysis confirmed of a 2-methyl-3-hydroxyl propanoyl substituent. A downfield shift at C-6″ (δ 63.90) of the glucopyranosyl residue in the 13C NMR
Natural Product Research
3
4''' 3''' 2'''
OH
OH
O O
5''
4''
HO
2'
HO
O
H
6''
H
OH
3'
1'''
3''
H
O 1''
2''
OH
O
7
H
9
1'
5'
2 6'
10 6
H3CO
H
1
8
4'
3 4
5
OH
OH
O
1
Downloaded by [La Trobe University] at 03:19 04 February 2016
O HO
OH
O OH
O HO HO
HO
2
3
OH OH
O
OCH3
OH
O OH
O
HO
HO OH
4
OH
O
5
OH
6
Figure 1. Chemical structure of the compounds isolated from A. maritimus.
spectrum proved that this substituent was located at C-6 (Charia et al. 1977). The application of HMQC and HMBC experiments led to full assignments of the 1H and 13C NMR chemical shifts of compound 1. HSQC experiments which correlated all proton resonances with those of each corresponding carbon. In the HMBC spectrum, the pattern of 1H–13C correlation was observed between δ H 5.17 (H-1″) with δ C 156.6 (C-7) indicating a glucosyl moiety is attached to C-7. The HMBC and HSQC data confirmed the location of the propinyl unit at C-6″ through the observed correlations among H-6″ (δ 3.96, 4.44) and C-1″′ (δ 174.7). The substitution at C-2″′ by methyl and methine groups was confirmed by the long-range correlations between the protons of these groups and carbonyl group (δ 174.7). The positive cotton effect observable in the circular dichroism (CD) spectrum indicated that the absolute configuration at the 2″′-position of compound 1 was S. Based on the above data, compound 1 is deduced to be patuletin 7-O-β-D-[(2″′S) 6″(3″′-hydroxy-2″′-methyl-propanoyl)] glucopyranoside.
4
M. I. Ezzat et al.
Table 1. Acute anti-inflammatory activity of the ethanol extract of the flowering aerial parts of A. maritimus (L.) Less. % Oedema Group (n = 6) Control The ethanolic extract of A. maritimus Indomethacin
Dose mg/kg b.wt. 1 mL saline 100 20
Mean ± S.E. 59.4 ± 1.6 36.8 ± 1.3* 22.6 ± 0.4*
% of Change – 38 62
Potencya – 0.61 1
Downloaded by [La Trobe University] at 03:19 04 February 2016
Note: % of change calculated as regard the control group. a Potency calculated as compared to the standard anti-inflammatory drug Indomethacin. * p
