Anna Szakiel

Influence of environmental abiotic factors on the content of saponins in plants

Saponins occur constitutively in many plant species as part of their defense system. However, saponin content in plants seems to be dynamic, responding to many external factors including various biotic stimuli connected to herbivory attack and pathogenic infection, as well as involved in plant mutualistic symbioses with rhizobial bacteria and mycorrhizal fungi. Thus, not only saponins influence the living organisms interacting with plants, but in turn, all these interactions can impact the plant saponin content. According to their constitutive occurrence in plants, saponins are regarded mainly as phytoanticipins. Nevertheless, some presented data clearly point out to induced biosynthesis of saponins, especially in plant response to insect herbivory or inoculation with root symbionts, while the best studied examples of interactions between plants and their microbial pathogens show rather qualitative change of saponin composition based on chemical modifications of preformed, pre-infectional precursors. Simultaneously, despite evident inducibility of saponin production in plant cell cultures, the possible role of these compounds as phytoalexins synthesized in intact plants after pathogen infection is still not well documented. Some practical patterns and ecological consequences of biotic factors influencing saponin content in plants are briefly highlighted, with the special attention paid to microbial inoculants applied for optimisation of saponin synthesis in cultivated medicinal plants.

Fruit cuticular waxes as a source of biologically active triterpenoids

The health benefits associated with a diet rich in fruit and vegetables include reduction of the risk of chronic diseases such as cardiovascular disease, diabetes and cancer, that are becoming prevalent in the aging human population. Triterpenoids, polycyclic compounds derived from the linear hydrocarbon squalene, are widely distributed in edible and medicinal plants and are an integral part of the human diet. As an important group of phytochemicals that exert numerous biological effects and display various pharmacological activities, triterpenoids are being evaluated for use in new functional foods, drugs, cosmetics and healthcare products. Screening plant material in the search for triterpenoid-rich plant tissues has identified fruit peel and especially fruit cuticular waxes as promising and highly available sources. The chemical composition, abundance and biological activities of triterpenoids occurring in cuticular waxes of some economically important fruits, like apple, grape berry, olive, tomato and others, are described in this review. The need for environmentally valuable and potentially profitable technologies for the recovery, recycling and upgrading of residues from fruit processing is also discussed.

Antibacterial and antiparasitic activity of oleanolic acid and its glycosides isolated from marigold (Calendula officinalis).

The antibacterial and antiparasitic activities of free oleanolic acid and its glucosides and glucuronides isolated from marigold (Calendula officinalis) were investigated. The MIC of oleanolic acid and the effect on bacterial growth were estimated by A600 measurements. Oleanolic acids influence on bacterial survival and the ability to induce autolysis were measured by counting the number of cfu. Cell morphology and the presence of endospores were observed under electron and light microscopy, respectively. Oleanolic acid inhibited bacterial growth and survival, influenced cell morphology and enhanced the autolysis of Gram-positive bacteria suggesting that bacterial envelopes are the target of its activity. On the other hand, glycosides of oleanolic acid inhibited the development of L3 Heligmosomoides polygyrus larvae, the infective stage of this intestinal parasitic nematode. In addition, both oleanolic acid and its glycosides reduced the rate of L3 survival during prolonged storage, but only oleanolic acid glucuronides affected nematode infectivity. The presented results suggest that oleanolic acid and its glycosides can be considered as potential therapeutic agents.

Saponins in Calendula officinalis L. - structure, biosynthesis, transport and biological activity

Trends in research on Calendula officinalis L. saponins performed in Department of Plant Biochemistry at Warsaw University are reviewed. Calendula officinalis, a well known medicinal plant, contains significant amounts of oleanane saponins, which form two distinct series of related compounds, called “glucosides” and “glucuronides” according to the structure of the respective precursor. Both series differ in the pathway of their biosynthesis and further metabolism, i.e. the rate of formation and stages of possible degradation; distribution in the single cell and in the whole plant, including accumulation sites; and the possible physiological role played in the plant according to appropriate biological activities.

Comparison of the Triterpenoid Content of Berries and Leaves of Lingonberry Vaccinium vitis-idaea from Finland and Poland

Triterpenoid compounds extracted from fruits and leaves of lingonberry ( Vaccinium vitis-idaea L.) collected in Finland and Poland were identified and quantitated by GC-MS/FID. The main lingonberry triterpenoid profile consisted of α-amyrin, β-amyrin, betulin, campesterol, cycloartanol, erythrodiol, fern-7-en-3β-ol, friedelin, lupeol, sitosterol, stigmasterol, stigmasta-3,5-dien-7-one, swert-9(11)-en-3β-ol, taraxasterol, urs-12-en-29-al, uvaol, oleanolic acid, and ursolic acid. To our knowledge, this is the first thorough description of triterpenoid compounds in this species. Ursolic acid was identified as a principal triterpene in lingonberry fruit. The influence of geographical origin on the level of individual triterpenoid compounds was examined, and considerable variations in triterpenoid profile between berries and leaves obtained from the two locations were observed. The most striking difference concerned the occurrence of fernenol and taraxasterol, which were found to be the major triterpenol in lingonberry leaves of Finnish and Polish origin, respectively.

Triterpenoid Content of Berries and Leaves of Bilberry Vaccinium myrtillus from Finland and Poland

Triterpenoid compounds found in free and ester forms in extracts of entire fruits and leaves and in fruit and leaf cuticular waxes of bilberry (Vaccinium myrtillus L.) collected in Finland and Poland were identified and quantitated by gas chromatography-mass spectrometry coupled to a flame ionization detector (GC-MS/FID). The main bilberry triterpenoid profile consisted of α- and β-amyrin, α- and β-amyrenone, campesterol, cholesterol, citrostadienol (in berries), cycloartanol, erythrodiol, lupeol, 24-methylenecycloartanol, sitosterol, sitostanol, stigmasterol, stigmasta-3,5-dien-7-one, uvaol, oleanolic and ursolic aldehydes, and oleanolic, ursolic, 2α-hydroxyoleanolic, and 2α-hydroxyursolic acids. Friedelin and D:A-friedooleanan-3β-ol were found only in Finnish plants, whereas D:C-friedours-7-en-3β-ol and taraxasterol were found only in Polish plants. To our knowledge, this is the first thorough description of triterpenoid compounds in this species. The presented results revealed that the triterpenoid profile of bilberry varied considerably between different organs of the plant, regardless of the plant origin, as well as between plant samples obtained from the two geographical locations.

Triterpenoid profile of flower and leaf cuticular waxes of heather Calluna vulgaris

Analysis of the main triterpenoid profile of chloroform-soluble cuticular waxes of heather flowers and leaves by GC–MS revealed the following composition: five triterpene acids – betulinic, oleanolic, ursolic, 3-oxo-olean-12-en-28-oic and 3-oxo-ursan-12-en-28-oic; eight monohydroxyalcohols – α-amyrin, β-amyrin, cycloartanol, 24-methylenecycloartanol, friedelinol, germanicol, lupeol and taraxasterol; three dihydroxyalcohols – betulin, erythrodiol and uvaol; two aldehydes – oleanolic and ursolic; four ketones – α-amyrenone, 4-epi-friedelin, friedelin and taraxerone and seven steroids – campesterol, cholesterol, sitostanol, sitosterol, stigmasterol, stigmasta-3,5-dien-7-one and stigmastane-3,6-dione. Triterpenoids accounted for 20% and 65% by mass of flower and leaf waxes, respectively, which suggest that heather leaves represent a very promising source of these compounds. Ursolic acid was the principal triterpenoid in the cuticular wax of both organs, whereas among the neutral triterpenes, friedelin and uvaol were the most abundant in flowers and leaves, respectively. This report provides the first thorough overview of the triterpenoid composition of cuticular waxes of heather.

Distribution of oleanolic acid glycosides in vacuoles and cell walls isolated from protoplasts and cells of Calendula officinalis leaves

The contents of oleanolic acid and its 3-0-glucuronide derivatives as well as of 3-0-glucoside derivatives were determined in vacuoles prepared from protoplasts and cell walls obtained from cells of Calendula officinalis leaves. In both cell compartments studied 37% of total cellular oleanolic acid were accumulated, 0.6% occurring as free oleanolic acid (only in vacuoles). Glucuronides accounted for 31.1% (20.7% in vacuoles and 10.4% in cell walls), and glucosides for 5.3% (2.6% in vacuoles and 2.7% in cell walls).

Metabolism of (3-3H)oleanolic acid in Calendula officinalis L. roots

The radioactive precursor, [3-3H]oleanolic acid was administrated to excised roots from four weeks old Calendula officinalis L. plants. Transformations of this compound into two series of its glycosides, i.e. glucosides and glucuronides were investigated. For the first time it has been shown that both series of oleanolic acid glycosides are synthesized in roots of young marigold plants. The pathway of their biosynthesis seems to be similar, although not identical, to the pathway occurring in green organs of C. officinalis.

The mechanism of oleanolic acid monoglycosides transport into vacuoles isolated from Calendula officinalis leaf protoplasts

Abstract The uptake of [3- 3 H]-oleanolic acid 3- O -monoglucoside and 3- O -monoglucuronide into vacuoles isolated from Calendula officinalis leaf protoplasts was investigated under various conditions. The transport of monoglucoside was stimulated by ATP and pyrophosphate, and sensitive to protein-modifying agent as well as dissipaters of the membrane potential. On the contrary, the transport of monoglucuronide was not dependent on tonoplast energization and was affected only by a protein-modifying factor. Moreover, the kinetics of tonoplast transport of both monoglycosides was characterized as concentration-dependent with saturation phase. The obtained results indicate that oleanolic acid monoglucoside is transported to isolated vacuoles by an active, carrier-mediated and energy-dependent mechanism, whereas the transport of monoglucuronide is a passive, carrier-mediated process.