Evaluation of Coleus forskohlii Genotypes for Bio Chemical Characters
Coleus forskohlii Briq., belonging to the mint family Lamiaceae, is an important ancient root drug credited with various medicinal properties. The root extracts of C. forskohlii were found to contain forskolin and its therapeutic properties contributed to the emergence of C. forskohlii as a taxon of importance in modern medicine. Traditionally it is used for pickle making and as a condiment in India. Thirty seven C. forskohlii genotypes collected from various places of the important Coleus growing states viz., Tamil Nadu and Karnataka were evaluated for total sugars, starch and crude protein at Horticultural College and Research Institute, Tamil Nadu Agricultural University, Coimbatore to assess its suitability for edible purpose. The genotypes exhibited remarkable variations for all the characters studied. The total sugar, starch and crude protein content in the fresh tubers varied from 5.90 to 10.03 g, 6.97 to 20.94 g and 6.14 to 9.05 g per 100 g, respectively. The genotype CF 37 excelled in the accumulation of total sugars, starch and crude protein in tuber and thus can be utilized for medicinal as well as edible purposes.
Coleus forskohlii Briq. syn. C. barbatus Benth, is an indigenous
medicinal plant and this ancient root drug is recorded in Ayurvedic Materia
medica under the Sanskrit name Makandi and Mayani (Shah,
1996). It is used widely against various disorders viz., antiaging, antioxidant
and a remedy for heart, abdominal and respiratory disorders (Ammon
and Muller, 1985; De Souza and Shah, 1988). It is
common on dry, barren hills and it is cultivated in India for its roots which
contains the active principle, forskolin (7 β-acetoxy-8, 13-epoxy-1α,
6 β, 9 α-trihydroxylabd-14-en-11-one) and the presence of which is
exclusive to this particular species (Shah et al.,
1980; Abraham et al., 1988).
De Souza and Shah (1988) indicated that C. forskohlii
is the only known natural source of the diterpenoid forskolin. Coleus forskohlii
is used for pickle making and it is also used as a condiment. Since, forskolin
is highly used for curing diseases like glaucoma, intake of C. forskohlii
tuber through food will be highly beneficial. Hence, the present study was postulated
to access the total sugar, starch and crude protein content in the fresh tubers/roots
of the C. forskohlii genotypes collected and thereby to ascertain their
MATERIALS AND METHODS
A total of 37 genotypes collected from different places of Tamil Nadu and Karnataka
(Table 1) were grown in the field in a randomized block design
with two replications at the Botanical Garden, Tamil Nadu Agricultural University,
Coimbatore during 2005-06.
|| Coleus forskohlii genotypes subjected to evaluation
The terminal cuttings of 15 cm length were planted at a spacing of 60x45 cm.
As a prophylactic measure against root rot, the cuttings were dipped in 0.1%
Pseudomonas fluorescens for 15 min just before planting. The recommended
cultural practices along organic fertilization (vermicompost 2.5 t ha-1
and neemcake 1 t ha-1) and plant protection measures were followed
to raise an ideal crop. The roots were harvested at 180 days after planting
and fresh tubers/roots were used for the sugars, starch and crude protein estimation.
The amount of total soluble sugars and starch present in the tubers/roots were
estimated as per the anthrone method suggested by Sadasivam
and Manickam (1996). The nitrogen content in tubers/roots of genotypes was
estimated by Microkjeldhal's method as recommended by Humphries
(1956). From the nitrogen content, the crude protein was estimated by employing
the standard multiplication factor of 6.25. The statistical scrutiny of data
was done by adopting the standard procedures of Sukhatme and
The total sugars, starch and crude protein content in the tubers/roots of all the thirty seven C. forskohlii genotypes were determined and the results are presented in the Table 2. Significant difference was noticed between tuberous and non tuberous genotypes for all the parameters estimated.
|| Total sugar, starch and crude protein content (g per 100
g) of C. forskohlii genotypes
Tuberous genotypes registered higher values for total sugar content in tubers and among them, genotype CF 37 registered the highest total sugar content in tubers followed by the genotype CF 36 whereas the least total sugar content in tubers of 7.87 g/100 g was registered by CF 31. Genotypes CF 23 and 10 exhibited the highest and least values of 7.49 g/100 g and 5.90 g/100 g for total sugar content in roots among non tuberous genotypes.
The starch content of roots/tubers differed significantly among tuberous and non tuberous genotypes. The starch content of tubers was the highest in the genotype CF 37 which exhibited 20.94 g/100 g of fresh tuber followed by CF 36 (20.74 g/100 g). The least starch content of 18.25 g/100 g of fresh tuber was observed in the genotype CF 15. The least starch content of 6.97 g/100 g of fresh root was noticed in CF 2 among non tuberous genotypes. Maximum starch content of 7.72 g/100 g in the roots of genotype CF 14 was observed.
Similar to starch content, the tuberous genotypes recorded higher content of crude protein in tubers than the non tuberous genotypes. The genotype, CF 37 registered an increased crude protein content of 9.05 g/100 g followed by CF 36 which recorded 9.03 g/100 g (Table 2). The least crude protein content (7.85 g/100 g) was recorded by the genotype CF 22 among tuberous genotypes. The highest and least values of 6.95 and 6.14 g/100 g were recorded by genotypes CF 14 and 1, respectively among non tuberous genotypes.
According to Datta (1994), the first formed assimilate
in the plant will be the simple sugars which will be used for the plant metabolic
activities and the excess be stored in their reserve organs. In the present
study, tuberous genotypes accumulated more sugars in tubers than non tuberous
genotypes. Increased total sugars in tubers may be attributed to the high partitioning
efficiency and increased efficiency of the sink to accumulate assimilates in
the tuberous genotypes. Srivastava et al. (2002)
also reported similar finding in C. forskohlii ecotypes.
Datta (1994) reported that, if the simple sugars are
not used immediately, they are converted into polysaccharides, such as, starch
and cellulose. The bulk of polysaccharides will be stored in the reserve organs
in the solid state where they often show a high level of crystallinity, such
as, starch granules. In the present study, it was observed that non tuberous
genotypes had lower amount of starch in roots, whereas, in the tuberous genotypes,
accumulation of starch was more. Patil (2000) reported
that there are variations in the presence of starch granules in the mesophyll
tissues of C. forskohlii genotypes. If the relative low abundance of
starch grains in the leaf tissues is an indication of the efficient translocation
to the sink, the tuberous genotypes should be credited with high translocation
efficiency of the photosynthates to the sink (Patil, 2000).
Nanaiah (1993) observed genotypic differences with reference
to starch grain abundance in the mesophyll tissue and suggested that it was
genetically inherited. Kavitha et al. (2007)
concluded that tuberous genotypes accumulate more starch than non tuberous genotypes
by conducting microtome section analysis of leaf mesophyll tissues. The tuberous
genotypes varied among themselves for the starch content in tubers, which is
in consonance with in the findings of Srivastava et al.
(2002) in C. forskohlii ecotypes.
Protein is the immediate product of gene expression following transcription
and translation and in the present study, significant differences were observed
among genotypes for crude protein content in tubers. The variability in crude
protein among different clones in cassava had been well documented. In the present
study, the crude protein contents varied among the genotypes from 6.14 to 9.05
g/100 g. Similar genotypic variation for crude protein content in tubers was
also recorded in several other tuber crops viz., yam (Splittstoesser
et al., 1973), sweet potato (Purcell et al.,
1978), Coleus parviflorus (Lila and Bala, 1987)
and C. forskohlii (Srivastava et al.,
The results obtained from the present study revealed that the genotype CF 37
excelled in the accumulation total sugar, starch and crude protein. Earlier
it had been reported that the genotype 37 excelled in forskolin and essential
oil content accumulation (Kavitha et al., 2006).
Hence, it is concluded that the particular genotype may be exploited for medicinal
and edible purposes. The culture requires to be tested for tuber yield for commercial
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