3. FOOD ChEMISTRy & bIOTEChNOLOGy 3.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Food Chemistry & Biotechnology
P105 SEA buCKThORN – SOuRCE OF VITAMIN C
MILEnA VESPALCOVá a , DAnA VRánOVá a , JIřInA
EnDSTRASSEROVá a and VOJTěCH řEZníČEK b
a Faculty of Chemistry, Brno University of Technology, Institute
of Food Science and Biotechnology, Purkynova 118,
612 00 Brno,
b Faculty of Horticulture, Mendel University of Agriculture
and Forestry, Department of Breeding and Propagation of
Horticultural Plants, Valtická 337, 691 44 Lednice,
vespalcova@fch.vutbr.cz
Introduction
Sea buckthorn (Hippophae rhamnoides) is a bush giving
small orange fruits. The bush comes from Asia but it has
spread almost all over the world during last century because
it can be grown even in harsher climate conditions without
special agrotechnical technology. The largest producers of
sea buckthorn are China, Russia, Finland and Germany at
present.
Sea buckthorn has been used as a natural drug in Asia
to treat heart diseases, digestive tract diseases, cough, etc.
Today, sea buckthorn extract is added not only in homeopathic
remedies and food supplements, but also into syrups,
jams, sweets, oils, face creams, shampoos, soaps, teas and
many other products all over the world. Sea buckthorn contains
many substances beneficial to human health, particularly
vitamin C in amount larger than in other kinds of fruit or
vegetable. Among other substances, also carotenoids, flavonoids,
essential unsatured fatty acids and phytosterols should
be mentioned. Their content depends not only on individual
genotypes and cultivars of this plant but also on the site at
which the plant is growing. This, naturally, holds also for the
vitamin C, which frequently serves as one of basic indicators
of alimentary and economical attractivity of planted sea buckthorn
cultivars.
The aim of the presented work is therefore the comparison
on the vitamin C content in the sea buckthorn cultivars
and genotypes growed by Faculty of Horticulture, Mendel
University of Agriculture and Forestry Brno. Two methods
have been applied for the determination of the vitamin C
content in the sea buckthorn juice: HPLC with photometric
detection and the direct coulometric determination of the
vitamin C.
Fig. 1. Analysis of the Vitaminová cultivar
s813
Experimental
T h e H P L C D e t e r m i n a t i o n
The Liquid chromatograph Spectra System equipped
with the UV 6000 LP detector and the Chromquest software
(Thermo Separation Products, USA) were used. for analyses
of sea buckthorn juices prepared from the sea buckthorn
cultivars as described below. The juices were injected on
the TESSEK Separon SGX RPS Column (TESSEK, Praha,
Czech Republic). The separation bed of 5 μm particles was
of 5 mm in diameter and of 250 mm in length. 0.01M oxalic
acid was the mobile phase. The column effluent was monitored
at 254 nm.
D i r e c t c o u l o m e t r y
The coulometric analyser PCA/C-Vit (ISTRAn, Bratislava,
Slovak Republik) equipped with porous working
electrode served for direct coulometric determination of vitamin
C without preliminary separation of the compound from
sea buckthorn juices. The determination utilizes oxidation of
ascorbic acid to dehydroascorbic acid
C 6 H 8 O 6 – 2e → C 6 H 6 O 6 + 2H + (1)
T h e P r e p a r a t i o n o f J u i c e s
We analysed 12 cultivars of sea buckthorn listed
in Table I. The cultivars were planted in the breeding station
of the Horticulture Faculty, Mendel University of Agriculture
and Forestry Brno in Žabčice. Fruits harvested October
4, 2006 were immediately freezed to –18 °C and stored
at this temperature in the freezing box till the analyses started
April 2007. Approximately 5 grams of dry fruits freely
warmed to room temperature was weighed to five digits and
homogenized in the mortar with small amount oxalic acid,
quantitatively transfered to the 100 ml volumetric flask by
2 % (w/v) solution of oxalic acid in water and than filled with
the acid solution to the division line. For chromatographic
analyses, aliquot part of solution was filtered using the Büchner
slit-sieve funnel and by cellulose 3-μm microfilter. The
filtered sample was enriched by the special reaction solution
R-020T (ISTRAn, Bratislava, Slovak Republic) for coulometric
analyses. The analysed sample were prepared daily
just before use and stored in dark during analyses.
Results and Discussion
A typical chromatogram of C vitamin analysis at conditions
specified in Experimental is given on at Fig. 1. Vitamin
C is in second peak, first peak is a mixture of unindentified
impurities.
Main validation parameters of successively repeated
chromatographic analyses are as follows: LOD and LOQ
of ascorbic acid is 0.2 and 0.7 mg dm –3 , respectively. Correlation
coefficient of ascorbic acid is R 2 = 0.9942 for the concentration
range of vitamin C from 0.0007 to 500 mg dm –3 .
Repeatability of analyses in concentration ranges
151–200 mg dm –3 , 51–150 mg dm –3 and 10–50 mg dm –3 given
by RSD vaules is 4 %, 6 % and 10 %, respectively. Mean
recovery of used analysis is 89.5 %. However, repeatability