5
were the major class found among the sesquiterpenoids, although bisabolanes, bakkanes, and other types of compounds were also obtained.
In this contribution are described phytochemical studies carried out by our
groups mainly from 2000 onward, inclusive of our results on the diversity in secondary metabolites of Ligularia growing in the Hengduan Mountains area, focusing
on eremophilane sesquiterpenoids and other metabolites. The present contribution
deals with 1049 compounds, not only those that were new when first characterized
but also known analogs, as isolated from Ligularia species. Genetic analyses, synthesis aspects, and biological activities will also be discussed.
In our own work, plants were collected from selected locations in Yunnan,
Sichuan, Qinghai, and Gansu Provinces, and Chongqing City, China. They were
identified by Dr. Xun Gong, Kunming Institute of Botany, China. The DNA
(ITS1-5.8S-ITS2) sequences were also investigated, as carried out by Prof. Ryo
Hanai, Rikkyo University, Tokyo Japan (see Sect. 4). Plant collection expeditions
have been conducted since the summer of 2000.
In this contribution, the plant names and their constituents will be tabulated for
each species, with the year of collection included if mentioned in the literature. In
the case of our own work, the first four digits provide the year of collection and the
latter two or three digits are specimen numbers for that year. Collection locations
and their elevation (m) are indicated, if known. For our own work, the county and
city/province are given (C = Chongqing, G = Gansu, Q = Qinghai, S = Sichuan,
Y = Yunnan; other provinces are spelled out in full). Chemical constituents were
grouped roughly into eight categories: (1) bicyclic eremophilanes (without ring C
and nor-eremophilanes); (2) 10H tricyclic eremophilanes (furans and lactones
(12,8-olides) with a hydrogen at C-10); (3) 10-OH tricyclic eremophilanes (furans
and lactones with a hydroxy group at C-10); (4) tricyclic eremophilanes with 1(10)ene, 9-ene, and 1,10-epoxide; (5) the cacalol group; (6) bakkanes and other sesquiterpenoids; (7) aromatics; and (8) others. Mono-, di-, and triterpenes are grouped
within the “others” category. The groups have been slightly changed for each table
depending on the species. The major constituents are underlined, if they were
described. In this work, alkaloids and sterols are not acquired.
Furanoeremophilanes can be detected by TLC using Ehrlich’s reagent. Thus,
their trisubstituted furan ring reacts with p-dimethylaminobenzaldehyde in the presence of HCl to show a yellow, pink, purple, or blue color, depending on the nature
of the substituent [15]. Examples are included in Plate 3. Preliminary TLC experiments may be conducted in a facile manner, so that diversity in chemical composition can be indicated without the isolation of each compound (Sect. 3.1). However,
because a TLC experiment does not yield any structural detail, conventional phytochemical analysis investigations, involving isolation and structure determination,
were also carried out.
Total ion chromatograms (TIC) of extracts were measured in LCMS analysis to
compare chemical constituents. Typical TICs are shown in Plate 4. For example,
these represent five chemotypes found in L. virgaurea. Although the V, C, N, and H
types are more or less continuous, typical samples show characteristic peaks corresponding to their representative compounds. By obtaining their LC-MS profiles, it
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…
were the major class found among the sesquiterpenoids, although bisabolanes, bakkanes, and other types of compounds were also obtained.
In this contribution are described phytochemical studies carried out by our
groups mainly from 2000 onward, inclusive of our results on the diversity in secondary metabolites of Ligularia growing in the Hengduan Mountains area, focusing
on eremophilane sesquiterpenoids and other metabolites. The present contribution
deals with 1049 compounds, not only those that were new when first characterized
but also known analogs, as isolated from Ligularia species. Genetic analyses, synthesis aspects, and biological activities will also be discussed.
In our own work, plants were collected from selected locations in Yunnan,
Sichuan, Qinghai, and Gansu Provinces, and Chongqing City, China. They were
identified by Dr. Xun Gong, Kunming Institute of Botany, China. The DNA
(ITS1-5.8S-ITS2) sequences were also investigated, as carried out by Prof. Ryo
Hanai, Rikkyo University, Tokyo Japan (see Sect. 4). Plant collection expeditions
have been conducted since the summer of 2000.
In this contribution, the plant names and their constituents will be tabulated for
each species, with the year of collection included if mentioned in the literature. In
the case of our own work, the first four digits provide the year of collection and the
latter two or three digits are specimen numbers for that year. Collection locations
and their elevation (m) are indicated, if known. For our own work, the county and
city/province are given (C = Chongqing, G = Gansu, Q = Qinghai, S = Sichuan,
Y = Yunnan; other provinces are spelled out in full). Chemical constituents were
grouped roughly into eight categories: (1) bicyclic eremophilanes (without ring C
and nor-eremophilanes); (2) 10H tricyclic eremophilanes (furans and lactones
(12,8-olides) with a hydrogen at C-10); (3) 10-OH tricyclic eremophilanes (furans
and lactones with a hydroxy group at C-10); (4) tricyclic eremophilanes with 1(10)ene, 9-ene, and 1,10-epoxide; (5) the cacalol group; (6) bakkanes and other sesquiterpenoids; (7) aromatics; and (8) others. Mono-, di-, and triterpenes are grouped
within the “others” category. The groups have been slightly changed for each table
depending on the species. The major constituents are underlined, if they were
described. In this work, alkaloids and sterols are not acquired.
Furanoeremophilanes can be detected by TLC using Ehrlich’s reagent. Thus,
their trisubstituted furan ring reacts with p-dimethylaminobenzaldehyde in the presence of HCl to show a yellow, pink, purple, or blue color, depending on the nature
of the substituent [15]. Examples are included in Plate 3. Preliminary TLC experiments may be conducted in a facile manner, so that diversity in chemical composition can be indicated without the isolation of each compound (Sect. 3.1). However,
because a TLC experiment does not yield any structural detail, conventional phytochemical analysis investigations, involving isolation and structure determination,
were also carried out.
Total ion chromatograms (TIC) of extracts were measured in LCMS analysis to
compare chemical constituents. Typical TICs are shown in Plate 4. For example,
these represent five chemotypes found in L. virgaurea. Although the V, C, N, and H
types are more or less continuous, typical samples show characteristic peaks corresponding to their representative compounds. By obtaining their LC-MS profiles, it
Chemical Constituents of Ligularia Species (Asteraceae) and Their Diversity…