radish

The plant family of Cruciferae contains many important vegetables of economic importance. Raphanus
sativus L. is originally from Europe and Asia. It grows in temperate climates at altitudes between 190 and
1240 m. It is 30–90 cm high and its roots are thick and of various sizes, forms, and colors (see Fig. 1).
They are edible with a pungent taste. Salted radish roots (Takuan), which are consumed in the amount of
about 500,000 tons/year in Japan, are essentially one of the traditional Japanese foods. The salted radish
roots have a characteristic yellow color, which generates during storage.
This specie is used popularly to treat liver and respiratory illnesses[1]. The antibiotic activity of its
extracts and its time persistence validates its effectiveness in microbial sickness as reported in traditional
medicine. The root’s juice showed antimicrobial activity against Bacillus subtilis, Pseudomonas
aeruginosa, and Salmonella thyphosa. The ethanolic and aqueous extracts showed activity against
Streptococcus mutans and Candida albicans. Aqueous extract of the whole plant presents activity against
Sarcinia lutea and Staphylococcus epidermidis[2]. Aqueous extract of the leaves showed antiviral effect
against influenza virus. Aqueous extract of the roots showed antimutagenic activity against Salmonella
typhimurium TA98 and TA100. In this review, the metabolites produced by R. sativus are presented
according to structural classes. (See also Tables 1 through 10 at the end of this paper.)

Alkaloids and Nitrogen Compounds
Alkaloid and nitrogen compounds present in the roots were pyrrolidine, phenethylamine, Nmethylphenethylamine, 1,2´-pyrrolidin-tion-3-il-3-acid-carboxilic-1,2,3,4-tetrahydro-β-carboline, and
sinapine[3,4,5]. Cytokinin (6-benzylamino-9-glucosylpurine) is a major metabolite of 6-
benzylaminopurine (6-BAP) in the root radish. A minor metabolite of 6-BAP from radish has been
identified as 6-benzylamino-3-β-D-glucopyranosylpurine[6]. Total amino acids were 0.5% of dry wt;
with proline (0.5%) as the major constituent, methionine and cystine were present in traces (0.02%).
Diamines as diaminotoluene (2,4-D), 4,4´-methylenedianiline (4,4-D), and 1,6-hexanediamine (1,6-D)
were isolated in the period of germination of young radish seeds. Production of thiamine is higher during
germination radishes[7].
Total protein was 6.5%[8]. Two chitinases, designated RRC-A and RRC-B, were isolated from radish
roots. Both compounds had a molecular weight of 25 kDa[9]. N-Bromosuccinimide and di-Etpyrocarbonate inhibited the activities of both chitinases.
Arabinogalactan proteins (AGPs) were isolated from primary and mature roots of the radish. These
were composed mainly of L-arabinose and D-galactose. Structures of the carbohydrate moieties of the root
were essentially similar to those isolated from seeds and mature leaves in that they consisted of
consecutive (1→3)-linked β-D-galactosyl backbone chains having side chains (1→6)-linked β-Dgalactosyl residues, to which α-L-arabinofuranosyl residues were attached in the outer regions. One
prominent feature of the primary root AGPs was that they contained appreciable amounts of L-fucose[10].

Two L-arabino-D-galactan–contained glycoproteins were isolated from the saline extract of mature
radish leaves; both contained L-arabinose, D-galactose, L-fucose-4-O-methyl-D-glucuronic acid, and Dglucuronic acid residues. Degradation of the glycoconjugates showed that a large proportion of the
polysaccharide chains is conjugated with the polypeptide backbone through a 3-O-D-galactosylserine
linkage[11].
Arabino-3,6-galactan associated with a hydroxyproline-rich protein portion and carried a unique
sugar residue, α-L-fucopyranosyl-(1-2)-α-L-arabinofuranosyl[12].
Stigma glycoproteins heritable with S-alleles (S-glycoproteins) were detected in R. sativus. Two main
glycoproteins appeared on the SDS-gel electrophoretic pattern. Their molecular weights were established
to be 15,000 and 100,000 Da. The carbohydrate fraction of the glycoprotein consisted of arabinose 17.3%,
galactose 19.1%, xylose 8.1%, mannose 5.4%, glucose 23.7%, and rhamnose or fucose 26.4%. In the
stigma surface diffusate of R. sativus, the content of protein was established to be 16% and that of
carbohydrate was 11%[13].
The R. sativus acanthiformis showed two ferredoxin isoproteins indicating that plants have multiple
genes for ferredoxin. The relative abundance of the isoproteins varied with leaf stage[14]. In the
isoprotein isolated from roots of the radish, the amino acid composition and N-terminal sequence were
different from those of radish leaf ferredoxin.
Polypeptides RCA1, RCA2, and RCA3 were purified from seeds of R. sativus. Deduced amino acid
sequences of RCA1, RCA2, and RCA3 have agreement with average molecular masses from electrospray
mass spectrometry of 4537, 4543, and 4532 kDa, respectively. The only sites for serine phosphorylation
are near or at the C terminal and hence adjacent to the sites of proteolytic precursor cleavage[15].
Cysteine-rich peptides (Rs-AFP1 and Rs-AFP2) isolated from R. sativus showed peptides 6, 7, 8, and
9 comprising the region from cysteine 27 to cysteine 47[16]. Protein AFP1 isolated from radish showed
peptide fragments (6-mer, 9-mer, 12-mer, and 15-mer)[17].
Proteins RAP-1 and RAP-2 were isolated from Korean radish seeds. The molecular mass of the two
purified was established to be 6.1 kDa (RAP-1) and 6.2 kDa (RAP-2) by SDS-PAGE and 5.8 kDa (RAP1) and 6.2kDa (RP-2) by gel filtration chromatography[17].