Triterpenoids are nature-derived compounds, broadly distributed in plant kingdom in a free form as well as in a form of
numerous glycosides. The complex structures of triterpenoids chiefly involve squalene derivatives, lanostanes, cycloartanes,
dammaranes, euphanes, tirucallanes, tetranortriterpenoids, quassinoids, lupanes, oleananes, friedelanes, ursanes, hopanes,
serratanes and another less known groups. These compounds present interesting and perspective subject for experiments,
chemical and biological as well. As it is known from literature data, triterpenoids and their saponins with respect to their
multitude pharmacological activities could be involved in several areas such as chemistry, medicine and pharmacology,
biomedicine and agrochemical sciences. The special structure of triterpenic skeletons allows to perform numerous chemical
transformations in order to obtain many new derivatives with pharmacological activity. Taking under consideration the above
data, chemistry, biology and pharmacology of triterpenoids and their saponins appear to be riped for revisiting. Therefore, this
special issue aims to review the advances in triterpenoids science during the last decade.
Carcinomas are probably the second leading cause of death in humans, so scientists intense their research upon the
development of new biological sources with antitumor activity. Medicinal plants are now the most promising sources of new
potent substances in cytotoxic drug development. As Csuk presented in his work, such compound of anticancer activity is
glycyrrhetinic acid, obtained e.g. from liquorice, known as sweetwood (Glycyrrhiza glabra) and some derivatives obtained
from this triterpenic acid.
Antitumor activity also exhibits, as presented by Paduch and Kandefer-Szerszeń, other triterpenes, such as: asiatic acid,
betulinic acid, boswellic acid, lupeol, oleanolic acid or ursolic acid and their analogs and derivatives. These compounds exhibit
a cytotoxicity against a variety of tumor cell lines comparable to some clinically used drugs. Most of them also have important
antiviral properties, especially anti-HIV activity, which makes them potentially useful additives to current anti-HIV therapy.
Another group of triterpenoids with anticancer and antiviral activity is limonoids family, belonging to tetranortriterpenoids.
As Pękala and co-workers present, limonoids are a very valuable group of triterpenoids because of a wide spectrum of
biological properties, such as cytotoxic, antimalarial, anti-inflammatory, antifeedant, antiviral, neuroprotective, antimicrobial,
antibacterial, antifungal and other activities. Limonoids present rich variety of structures: until 2011, about 1300 limonoids with
more than 35 carbon frameworks had been isolated from four families (Meliaceae, Rutaceae, Simaroubaceae, and
Cneoraceae). The unique structural features of these terpenoids have attracted continuous attention of chemists and
Triterpenoids often occur as ingredients of daily diet or of herbal products used for therapeutic purposes. These
phytochemicals occur in nature in free form or as glycosylated compounds, known as saponins, due to their characteristic
foaming properties. Pharmacological activities of saponins are very broad and include numerous directions of action which
were discussed in many works. Podolak and Janeczko summarize pharmacological properties of natural, non-glycosylated
triterpenoids, that were reported over the last five years. The work discusses e.g. antimicrobial, cytotoxic, anti-inflammatory,
antinociceptive, antidiabetic, hepatoprotective, wound healing and other activities of triterpenoids, focusing on less known
Plants remain as the most viable source of triterpenoid saponins. As plants are the source of pharmacologically active
saponins and free triterpenoids, it is obvious that the development of new methodologies to improve saponin yields is a
significant issue. As Yendo et al. state in their work current challenges to improve triterpenoid saponin production including a
better understanding of the signal transduction pathways leading to their accumulation, isolation and heterologous expression of
biosynthetic genes, as well as structural and modeling studies of biosynthetic enzymes and their catalytic mechanisms.
Some triterpenoids and their semi-synthetic derivatives can be identified as potential therapeutics against neurodegenerative
diseases. Ruszkowski and Bobkiewicz-Kozlowska discuss the ability of celastrol, oleanolic acid, ursolic acid, asiatic acid,
erythrodiol, and some triterpenoid saponins to protect the brain against neurodegeneration and neuroinflammation processes.
The authors focus on triterpenoids as possible drugs to treat or slow the progression of neurodegenerative diseases such as
Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, amyotrophic lateral sclerosis and multiple sclerosis (MS).
Further, pharmacological activities of naturally-derived triterpenenoids and some of their synthetic derivatives are discussed
by Jeong and Bae, Jaworska-Paszel et al. and by Luo et al.
The anti-inflammatory effect is a common property of many triterpenoids. Jeong and Bae discuss the anti-inflammatory
property of several triterpenoids derived from natural sources and from chemical synthesis. These triterpenoids include avicins,
boswellic acid, celastrol, diosgenin, escin, ginsenosides, glycyrrhizin, lupeol, oleanolic acid, platycodon D, saikosaponins,
ursolic acid, 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), and some of their derivatives. Jaworska-Paszel et al.
describe anti-inflammatory, antioxidative, antitumor, antileukemic, hepatoprotective, gastroprotective, cardioprotective and
many other important pharmacological activities of oleanolic acid. Luo et al. focus on recent advances in enone and NOreleasing
derivatives of oleanolic acid with anti-cancer activity.
Other compounds exhibiting numerous pharmacological activities are betulin and betulinic acid, both with pentacyclic
lupane-type skeleton. Betulin, betulinic acid and their derivatives have been studied in the last decades for their diversified
pharmacological activities like anti-HIV, anticancer, antibacterial, anti-inflammatory and many others. In the last few years,
great progress had been made on the synthesis and biological activity of triterpenoids derived from betulin and betulinic acid.
Shi and co-workers discuss recent research and development in chemistry of betulin and betulinic acid and present recent
modification within A-ring, E-ring, both, at the C-3 and at the C-28 position as well as at the C-30 position of betulin and
betulinic acid. The authors also present methods of conjunction of the above triterpenes with drugs.
Supercritical fluid extraction has been a widely studied green technology to obtain triterpenoids enriched extracts from
various vegetable matrices. De Melo and co-workers discuss research advances regarding the supercritical fluid extraction of
triterpenoids in terms of biomass sources, operating conditions and their optimization, and modeling. The authors provide
overview concerning the recent works (both publications and patents) upon supercritical fluid extraction of plant material
leading to triterpenoids with the most important experimental and/or theoretical information.
Many families of bioactive natural products are usually extracted from numerous plant sources in low yields. Triterpenic
acids belong to a group of the most often studied compounds, mainly because of their abundance in a large number of food and
medicinal plants. Domingues et al. in their work present overview of the biogenetic origin of some triterpenic acids, on the
analytical extraction and hyphenated methodologies (mainly GC-MS) used on their identification and quantification. The
authors also present an overview of the major sources of some triterpenic acids, indicating their potential large scale production
pathways, with especial emphasis on abundant agroforestry biomass residues. The future perspectives towards improved
therapeutic strategies using these triterpenic acids are also discussed herein.
The root bark of the Chinese medicine Tripterygium wilfordii contains a quinone methide triterpenoid - celastrol. Literature
data presents, that celastrol is one of the most potent antitumor activity compounds among the natural triterpenoids. Salvador et
al. discuss different mechanisms of antitumor activity of celastrol, such as abilities of inhibing proliferation, inducing apoptosis
and suppressing invasion and metastasis of tumor cells. The authors also describe the anticancer property of semi-synthetic
celastrol derivatives. As they noticed, the quinone methide moiety is required for its antitumor activity.
I thank all the contributors or this special issue and hope that the progresses highlighted in the topics covered will inspire
more research in this challenging area of organic synthesis. I thank Prof. Atta-ur-Raman for the kind invitation to be the Guest
Editor of this issue and all the reviewers for their time and valuable comments. I also thank Ms. Hina Wahaj (Publications
Manager, Bentham Science Publishers) for the help in organizing this issue.