The extraction of rutin from ¯ower buds of Sophora japonicaSchool of Natural and Environmental Sciences, Coventry University, Coventry CV1 5FB, UK Abstract The eciency of extraction of
Trang 1The extraction of rutin from ¯ower buds of Sophora japonica
School of Natural and Environmental Sciences, Coventry University, Coventry CV1 5FB, UK
Abstract
The eciency of extraction of rutin from Sophora japonica is improved by ultrasound but is dependent on the solvent employed Rutin is a compound with antioxidant activity and aqueous solvents appear to be unsuitable for ultrasonic extractions due to the formation of free radicals from the insonation of the solvent The application of ultrasound to methanolic extraction gave a sig-ni®cant reduction in extraction time and an increase in maximum yield Ó 2001 Elsevier Science B.V All rights reserved
Keywords: Rutin; Extraction; Ultrasound; Antioxidant
1 Introduction
Renewed interest in plant derived drugs has led to an
increased need for ecient extraction methods The aim
of this study was to compare conventional and
ultra-sonic methods for the extraction of the ¯avonoid, rutin
(Fig 1) from the dried ¯ower buds of the Chinese
Scholar Tree (Sophora japonica) [5]
Flavonoids are products of secondary metabolism in
plants and are of interest to the pharmaceutical and
food industries because of their reported antioxidant
activity [1] Such compounds can interact with free
radicals and so prevent the damage which radicals might
otherwise cause to cell membranes and biological
mol-ecules such as DNA
Ultrasound has been shown to aid extraction in a
number of plant materials by signi®cantly reducing
ex-traction times and increasing maximum exex-traction
yields An example is the extraction of helicid, a Chinese
medicine used in the treatment of fatigue and
listless-ness, from the dried seeds of Helicid erraticum using
aqueous ethanol [2] Conventional extraction is usually
performed at re¯ux temperature of 80°C for 2 h
Ul-trasonic at 40°C resulted in a yield increase of 50% in the
shorter time of 1 h Studies on the eect of ultrasound
on the extraction of the main components of sage
(Salvia ocinalis) showed that cineole, thujone and
borneol could be extracted better when sonicated [3]
Many other examples have been reviewed recently [4]
This observed enhancement of extraction of organic compounds by ultrasound is attributed to the pheno-menon of cavitation produced in the solvent by the passage of an ultrasonic wave During the rarefaction cycle of the sound wave cavitation bubbles are produced which ®ll with solvent vapour During the compression cycle the bubbles and the gas within them are also compressed resulting in a signi®cant increase in tem-perature and pressure This ®nally results in the collapse
of the bubble with a resultant Ôshock waveÕ passing through the solvent and enhanced mixing occurring Ultrasound also exerts a mechanical eect, allowing greater penetration of solvent into the plant body This, coupled with enhanced mass transfer and signi®cant disruption of cells, via cavitation bubble collapse, has the eect of releasing cell contents into the bulk medium Ultrasound may also produce some chemical eects due to the production of free radicals within the cavi-tation bubbles Sonication of water results in the for-mation of highly reactive hydroxyl radicals which can combine to form hydrogen peroxide which may or may not be bene®cial to the extraction process itself
2 Results and discussion Conventional extraction methods using dilute aque-ous alkali and methanol as solvents were compared with ultrasonic extractions in the same solvents In aqueous extractions ultrasonic methods were found to give re-duced yields when compared with conventional methods
as shown in Fig 2
Ultrasonics Sonochemistry 8 (2001) 299±301
www.elsevier.nl/locate/ultsonch
* Corresponding author.
E-mail address: l.paniwnyk@coventry.ac.uk (L Paniwnyk).
1350-4177/01/$ - see front matter Ó 2001 Elsevier Science B.V All rights reserved.
PII: S1350-4177(00)00075-4
Trang 2The observed reduction in extraction yield is believed
to be the result of degradation of the rutin by interaction
with highly reactive hydroxyl radicals formed during
sonication of the aqueous solvent The extractions were
therefore carried out in methanol, a solvent which does
not give rise to such a large proportion of radicals under
cavitation Experiments were performed at room
tem-perature without allowing the temtem-perature to rise since
(a) cavitational eects are reduced as temperature is
increased and (b) although the solubility of rutin in
methanol is much higher than in water over the whole
temperature range the dierence is particularly
signi®-cant at lower temperatures
Conventional methanolic extractions gave much
higher yields than aqueous extractions and the yields
were further enhanced by the use of ultrasonic
extrac-tion methods as shown in Fig 3
The higher yields obtained from conventional
meth-anolic extractions are attributed to the much greater
solubility of rutin in methanol than in water and its
apparent stability to air oxidation in this solvent The
further increase in yield when ultrasound is applied is
believed to be due to the disruption of cell walls by
ca-vitational eects Since hydrogen peroxide is not formed
during sonication of methanol the extracted rutin is not degraded
3 Experimental methods The conventional and ultrasonic methods employed are summarised as follows:
3.1 Aqueous extractions Ten grams of dried ¯ower buds were crushed using a pestle and mortar and mixed with water (100 cm3) The
pH was adjusted to 6±8 using 1 M NaOH and the mixture was either boiled (for conventional extraction)
or subjected to ultrasound (for ultrasonic extraction) using a 20 kHz ultrasonic probe (Sonics and Material-sVC600 with 0.5 in tip) at 23°C for varying lengths of time The mixture was ®ltered and the ®ltrate was acidi®ed (pH 5±6) using 1 M HCl to precipitate the rutin and left to stand overnight The precipitate was collected by vacuum ®ltration and dissolved in water and further puri®ed as follows The pH was adjusted to 6±8 and the solution was boiled for 30 min It was ®l-tered under vacuum and the ®ltrate was acidi®ed and left to stand overnight The resulting precipitate was collected by vacuum ®ltration and dried in an oven at 70°C
3.2 Alcoholic extractions Ten grams of dried ¯ower buds were crushed using a pestle and mortar and mixed with methanol (100 cm3) The mixture was either re¯uxed (for conventional traction) or subjected to ultrasound (for ultrasonic ex-traction) using a 20 kHz ultrasonic probe at 23°C for varying lengths of time The mixture was ®ltered and the solvent removed using a rotary evaporator The residue,
Fig 3 Eect of ultrasound on the extraction of rutin from Sophora japonica using methanol.
Fig 1 Structure of rutin.
Fig 2 Eect of ultrasound on the extraction of rutin from Sophora
japonica using water.
300 L Paniwnyk et al / Ultrasonics Sonochemistry 8 (2001) 299±301
Trang 3containing rutin alcoholate, was dissolved in water to
convert it into the hydrated form which precipitated
from solution The mixture was extracted with diethyl
ether to remove chlorophyll and the precipitate in the
aqueous phase was collected by vacuum ®ltration and
dried in an oven at 70°C
4 Conclusions
In any extraction process consideration must be given
to the solubility of the compound being extracted in the
chosen solvent at the extraction temperature employed
In the cases of compounds with antioxidant activity,
such as rutin, aqueous solvents appear to be unsuitable
for ultrasonic extractions and care must be taken when
employing aqueous solvents in order to avoid
degrada-tion of the sample
The application of ultrasound to the methanolic
ex-traction of rutin from Sophora japonica gave a
signi®-cant increase in maximum extraction yield
Acknowledgements The authors thank the EC for ®nancial support (COPERNICUS research program ERB-CIPA-CT94-0227-1995)
References
[1] J.Q Griths, C.F Krewson, J Naghski, Rutin and Related Flavonoids; Chemistry, Pharmacology and Clinical Applications, Mack Publishing., Easton, Pennsylvania, 1955.
[2] Y Zhao, C Bao, T.J Mason, A study of the isolation of eective compositions from traditional Chinese medicinal plants, Ultrason-ics International 91 Proceedings, Butterworths, 1991, pp 87±90 [3] M Salisova, S Toma, T.J Mason, Comparison of conventional and ultrasonically assisted extractions of pharmaceutically active compounds from Salvia ocinalis, Ultrason Sonochem 4 (1997) 131±134.
[4] M Vinatoru, M Toma, T.J Mason, Ultrasonically assisted extraction of bioactive principles from plants and their constitu-ents, In: T.J Mason (Ed.), Advances in Sonochemistry, vol 5, JAI Press, ISBN 0-7623-0331-X, 1999, pp 209±248.
[5] E Beaufoy, The extraction of rutin from Sophora japonica Using Ultrasound, M.Sc Thesis, Coventry University, 1998.
L Paniwnyk et al / Ultrasonics Sonochemistry 8 (2001) 299±301 301