A New Diglycoside of Diterpene from Ageratina vacciniaefolia

Pontificia Universidad Javeriana, Grupo de Investigación Fitoquímica GIFUJ, Santafé de Bogotá, Colombia
Phone: 3208320, fax 2850503, E-mail [email protected]

Received: 19 March 1999 / Published: 16 April 1999

From leaves and flowers of Ageratina vacciniaefolia [1-7] we have isolated several compounds: a flavonoid, a diterpene [8] and a new compound identified as b-D-glucopyranosil ester of (-)17-(b-glucopiranosyloxyl)-16-hydroxy-kauran-19-oic acid (see the formula). The structure was established by using ¹HNMR, ¹³CNMR, COSY, NOESY and HMBC spectroscopic techniques (Table 1) [1,7].

The ¹³CNMR spectrum showed totally 32 signals, 12 of them at ca. 62-99 ppm which are characteristic of glycoside. The rest 20 signals are attributed to the aglicone which is a compound of diterpene kaurane type,  and the structure has been confirmed by both ¹³CNMR and ¹HNMR spectra.

The signals from ¹HNMR at d 4.48 ppm (d, J=7.2 Hz) was assigned to the anomeric proton, whcih  has a direct correlation with C of d 98.45 ppm indicating a b-glycoside; while ¹HNMR signals appear at d 5.434 ppm (d, J= 7.2 Hz) coupling directly with C at d 95.56 ppm can be attributed to a b-glucose ester. Furthermore, the absence of signals to vinilic protons and the absence of signals to C9 and C15 connected to oxygen, similar to those in the other compound [8], indicate that this aglicone compound is a Kaurane derivative. The signal from ¹³CNMR spectrum at d 63.60 ppm showed a -CH₂OH connected to C17 which was confirmed by correlation observed on HMBC and NOESY spectra. A signal at d 91.55 ppm indicating a glucose connected to C16 is confirmed by a long range correlation on HMBC spectrum. An enzymatic hydrolysis of this compound with b-glucosidase also confirmed the structure purposed.

In summary, this compound was identified as b-D-glucopyranosil ester of (-)17-(b-glucopiranosyloxyl)-16-hydroxykauran-19-oic acid by using HNMR and ¹³CNMR spectra analysis and enzymatic hydrolysis with b-glucosidase [7].

The ethanolic extract from leaves and flowers of A. vacciniaefolia yielded white crystals after column chromatography and eluted with CH₂Cl₂, EtOAc and mixtures of these solvents. The compound was purified further by column chromatography on RP-18 eluted with MeOH-H₂O (2:1).

M.p. 198ºC.

[a]²⁰_D = -52.5 (0.0043 MeOH).

DCIMS [isobutane] m/z: 499; 481; 463; 419; 392; 391; 361; 319; 273; 163; 145 (100%); 127.

¹HNMR (360 MHz, CD₃OD): d in ppm, 0.96 (s, 3H, CH₃); 1.20 (s, 3H, CH₃);1.45 (m, 1H); 1.85 (m, 1H); 2.25 (m, 1H); 3.18 (m, 1H); 3.33 (m, 1H); 3.37 (m, 2H); 3.7 (dd, 1H, J=12.3Hz); 3.8 (dd, 1H, J=12.2 Hz); 4.48 (d, 1H, J=7.2 Hz, anomeric proton); 5.43 (d, 1H J=7.2, anomeric proton).

¹³CNMR (90.5 MHz, CD₃OD): d 16.38 (-CH₃, C); 19.71; 29.05 (-CH₃, C); 20.12; 25.17; 26.82; 37.62; 39.05; 40.92; 41.84; 43.07; 44.21; 45.08; 45.97; 51.40; 57.29; 58.54; 62.40; 62.52 (-CH₂OH); 63.60 (-CH₂-O-); 71.10; 71.42; 74.08; 75.18; 77.73; 78.29; 78.64 (2C); 91.55; 95.56; 98.45; 178.16 (-COO, C19). For details, see the following table (Table 1).

Acknowledgments: Project code 1203-05-394-95, CT-128-97, supported by COLCIENCIAS.

References

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