209
areas were grouped into two clades, A and B. The chemical compositions of these
samples could be grouped into two types, the furan ring-producing (F) and nonfuran ring-producing (N) types (Sect. 3.6 and Table 8). However, in contrast to
L. virgaurea, the chemotypes and the genetic clades did not necessarily correspond
to each other [22]. In addition, later, two additional samples were found that were
furan ring-producing specimens but did not belong to either clade A or B [31].
These data indicate that the diversity among L. kanaitzensis samples is complex.
Analyses of the ITS sequences were especially useful for hybrid samples (Sect.
3.37). Some samples of hybrids between L. subspicata (or L. lamarum) and
L. cyathiceps showed different parameters from each other in terms of morphology,
chemical composition, and ITS sequences. Specifically, the ITS sequences of one
sample (sample 6 in Sect. 3.37) were identical to those of L. cyathiceps, while, in
sample 7, the phytochemical profile was close to that of L. cyathiceps [38]. Sample
15 of L. lamarum (Sect. 3.29) was shown to be a hybrid with L. cyathiceps in the
ITS sequence [38]. Sample 7 of L. tsangchanensis (Sect. 3.35) was pure L. tsangchanensis in both its morphology and chemical composition but was a hybrid [25].
These results indicate that hybridization and backcrossing occur very often to
acquire the ability to produce a variety of compounds. Comparative analysis based
on two different aspects, chemical composition and neutral DNA sequencing, are
useful to better comprehend plant diversification.
Similar analyses have been carried out for other samples, including for L. anoleuca [154, 155], L. cyathiceps [17, 38], L. duciformis [36, 126], L. fischeri [37,
155], L. lamarum [23, 40, 115], L. melanothyrsa [21, 44], L. nelumbifolia [126,
127], L. oligonema [130], L. subspicata [24, 34, 38, 40, 127], L. veitchiana [154],
and L. vellerea [21, 25, 26], and for hybrid samples [18, 21, 25, 33, 38, 40, 127, 128,
150, 306].
5 Synthesis Aspects
Synthesis efforts toward eremophilane sesquiterpenoids have been carried out for a
long time, almost since they were first isolated from natural sources, because these
secondary metabolites have unique cis-1,2-arranged dimethyl groups and cisdecalin systems within their major groups. Historical work in this area has been
well documented in the literature [307–309]. In this contribution, the chemical synthesis of compounds isolated from Ligularia species is introduced briefly, in addition to various aspects covered on the synthesis aspects of compounds included in
Sect. 3.
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…
areas were grouped into two clades, A and B. The chemical compositions of these
samples could be grouped into two types, the furan ring-producing (F) and nonfuran ring-producing (N) types (Sect. 3.6 and Table 8). However, in contrast to
L. virgaurea, the chemotypes and the genetic clades did not necessarily correspond
to each other [22]. In addition, later, two additional samples were found that were
furan ring-producing specimens but did not belong to either clade A or B [31].
These data indicate that the diversity among L. kanaitzensis samples is complex.
Analyses of the ITS sequences were especially useful for hybrid samples (Sect.
3.37). Some samples of hybrids between L. subspicata (or L. lamarum) and
L. cyathiceps showed different parameters from each other in terms of morphology,
chemical composition, and ITS sequences. Specifically, the ITS sequences of one
sample (sample 6 in Sect. 3.37) were identical to those of L. cyathiceps, while, in
sample 7, the phytochemical profile was close to that of L. cyathiceps [38]. Sample
15 of L. lamarum (Sect. 3.29) was shown to be a hybrid with L. cyathiceps in the
ITS sequence [38]. Sample 7 of L. tsangchanensis (Sect. 3.35) was pure L. tsangchanensis in both its morphology and chemical composition but was a hybrid [25].
These results indicate that hybridization and backcrossing occur very often to
acquire the ability to produce a variety of compounds. Comparative analysis based
on two different aspects, chemical composition and neutral DNA sequencing, are
useful to better comprehend plant diversification.
Similar analyses have been carried out for other samples, including for L. anoleuca [154, 155], L. cyathiceps [17, 38], L. duciformis [36, 126], L. fischeri [37,
155], L. lamarum [23, 40, 115], L. melanothyrsa [21, 44], L. nelumbifolia [126,
127], L. oligonema [130], L. subspicata [24, 34, 38, 40, 127], L. veitchiana [154],
and L. vellerea [21, 25, 26], and for hybrid samples [18, 21, 25, 33, 38, 40, 127, 128,
150, 306].
5 Synthesis Aspects
Synthesis efforts toward eremophilane sesquiterpenoids have been carried out for a
long time, almost since they were first isolated from natural sources, because these
secondary metabolites have unique cis-1,2-arranged dimethyl groups and cisdecalin systems within their major groups. Historical work in this area has been
well documented in the literature [307–309]. In this contribution, the chemical synthesis of compounds isolated from Ligularia species is introduced briefly, in addition to various aspects covered on the synthesis aspects of compounds included in
Sect. 3.
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…