Occurrence of polygodial in species of Polygonum genus belonging to Persicaria section

Flavonoid, stilbene and diarylheptanoid constituents of Persicaria maculosa Gray and cytotoxic activity of the isolated compounds

Persicaria maculosa (Polygonaceae) has been used as edible and as medicinal plant since ancient times. As a result of multistep chromatographic purifications, chalcones [2'-hydroxy-3',4',6'-trimethoxychalcone (1), pashanone (2), pinostrobin chalcone (3)], flavanones [6-hydroxy-5,7-dimethoxyflavanone (4), pinostrobin (5), onysilin (6), 5-hydroxy-7,8-dimethoxyflavanone (7)], flavonol [3-O-methylgalangin (8)], stilbene [persilben (9)], diarylheptanoids [1,7-diphenylhept-4-en-3-one (10), dihydroyashabushiketol (12), yashabushidiol B (13)] and 3-oxo-α-ionol-glucoside (11) were isolated from P. maculosa. The present paper reports for the first time the occurrence of diarylheptanoid-type constituents in the family Polygonaceae. Cytotoxicity of 1-5, 7 and 9-11 on 4 T1 mouse triple negative breast cancer cells was assayed by MTT test. None of the tested compounds reduced the cell viability to less than 80% of the control. On non-tumorigenic D3 human brain endothelial cells the decrease of cell viability was observed in case of 1 and 2. Further impedance measurements on 4 T1 and D3 cells a concentration-dependent decrease in the cell index of both cell types was demonstrated for 1, while 2 proved to be toxic only on endothelial cells.

Identification of a drimenol synthase and drimenol oxidase from Persicaria hydropiper, involved in the biosynthesis of insect deterrent drimanes

The sesquiterpenoid polygodial, which belongs to the drimane family, has been shown to be an antifeedant for a number of herbivorous insects. It is presumed to be synthesized from farnesyl diphosphate via drimenol, subsequent C-12 hydroxylation and further oxidations at both C-11 and C-12 to form a dialdehyde. Here, we have identified a drimenol synthase (PhDS) and a cytochrome P450 drimenol oxidase (PhDOX1) from Persicaria hydropiper. Expression of PhDS in yeast and plants resulted in production of drimenol alone. Co-expression of PhDS with PhDOX1 in yeast yielded drimendiol, the 12-hydroxylation product of drimenol, as a major product, and cinnamolide. When PhDS and PhDOX1 were transiently expressed by agro-infiltration in Nicotiana benthamiana leaves, drimenol was almost completely converted into cinnamolide and several additional drimenol derivatives were observed. In vitro assays showed that PhDOX1 only catalyses the conversion from drimenol to drimendiol, and not the further oxidation into an aldehyde. In yeast and heterologous plant hosts, the C-12 position of drimendiol is therefore likely to be further oxidized by endogenous enzymes into an aldehyde and subsequently converted to cinnamolide, presumably by spontaneous hemiacetal formation with the C-11 hydroxyl group followed by oxidation. Purified cinnamolide was confirmed by NMR and shown to be deterrent with an effective deterrent dose (ED50 ) of about 200-400 μg g-1 fresh weight against both whiteflies and aphids. The putative additional physiological and biochemical requirements for polygodial biosynthesis and stable storage in plant tissues are discussed.

Comparison of the chemical composition of three species of smartweed (genus Persicaria) with a focus on drimane sesquiterpenoids

The genus Persicaria is known to include species accumulating drimane sesquiterpenoids, but a comparative analysis highlighting the compositional differences has not been done. In this study, the secondary metabolites of both flowers and leaves of Persicariahydropiper, Persicariamaculosa and Persicariaminor, three species which occur in the same habitat, were compared. Using gas chromatography-mass spectrometry (GC-MS) analysis of extracts, overall 21/29 identified compounds in extracts were sesquiterpenoids and 5/29 were drimanes. Polygodial was detected in all species, though not in every sample of P. maculosa. On average, P. hydropiper flowers contained about 6.2 mg g FW(-1) of polygodial, but P. minor flowers had 200-fold, and P. maculosa 100,000 fold lower concentrations. Comparatively, also other sesquiterpenes were much lower in those species, suggesting the fitness benefit to depend on either investing a lot or not at all in terpenoid-based secondary defences. For P. hydropiper, effects of flower and leaf development and headspace volatiles were analysed as well. The flower stage immediately after fertilisation was the one with the highest content of drimane sesquiterpenoids and leaves contained about 10-fold less of these compounds compared to flowers. The headspace of P. hydropiper contained 8 compounds: one monoterpene, one alkyl aldehyde and six sesquiterpenes, but none were drimanes. The potential ecological significance of the presence or absence of drimane sesquiterpenoids and other metabolites for these plant species are discussed.

Comparative study on the larvicidal activity of drimane sesquiterpenes and nordrimane compounds against Drosophila melanogaster til-til

Natural compounds from Drimys winteri Forst and derivatives exhibited larvicidal effects against Drosophila melanogaster til-til. The most active compound was isodrimenin (4). The highest lethal concentration to the larvae of D. melanogaster was 4.5 ± 0.8 mg/L. At very low concentrations drimenol (1), confertifolin (3), and drimanol (5) displayed antifeedant and larvae growth regulatory activity. The antifeedant results of nordrimanic and drimanic compounds were better in first instar larvae. The EC₅₀ value of polygodial (2) was 60.0 ± 4.2 mg/L; of diol 15 45.0 ± 2.8 mg/L, and of diol 17 36.9 ± 3.7 mg/L, while the new nordrimane compound 12 presented a value of 83.2 ± 3.5 mg/L.

Influence of plant part, season of collection and content of the main active constituent, on the antifungal properties of Polygonum acuminatum Kunth

ETHNOPHARMACOLOGICAL RELEVANCE

Polygonum acuminatum Kunth. (Polygonaceae) is used to heal infected wounds and as antifungal in the traditional Argentinean medicine.

AIM OF THE STUDY

The present investigation was carried out to evaluate the antifungal properties of aerial parts of Polygonum acuminatum, in order to give support to its ethnopharmacological use as antifungal agent and to isolate the compound(s) responsible for the antifungal properties. The influence of the plant part used, the season of the year and a study of the correlation of the antifungal activity with the content of the main active constituent were investigated too, with the aim of contributing to determine the most suitable plant extract and season of the year for achieving the best antifungal properties for Polygonum acuminatum traditional use.

MATERIALS AND METHODS

For the antifungal evaluation, the microbroth dilution assay recommended by the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS) was used against a panel of human opportunistic and pathogenic fungi. Bioassay-guided fractionation allowed us to isolate the compounds responsible for the antifungal activity. GC-MS was used to quantify the main component in the different extracts. For the statistical analysis, ANOVA test for analyses of variance followed by the Tukey test of Multiple Comparisons were used. The correlations between content of the antifungal compound and antifungal activity, were calculated with the Spearman Correlation Coefficient.

RESULTS

Aerial parts (A) of Polygonum acuminatum showed to possess antifungal properties against yeasts as well as dermatophytes but not against Aspergillus spp. From the most active extract (ADCM), polygodial, isopolygodial, drimenol and confertifolin were isolated, possessing polygodial a broader spectrum of action and lower MICs than the rest of compounds. Among the different parts, leaves (L), stems (S) and fruits (F), that constitute the aerial parts of Polygonum acuminatum, (L) showed to possess the best activities, compared to (S) and (F). The analysis of the content of polygodial in the LHex, LDCM, LEtOAC, LMeOH extracts collected in Summer, Autumn, Winter and Spring showed that LDCM of all seasons possessed higher percentages of this sesquiterpene than the rest of extracts. Among the LDCM of different seasons, that of Autumn was the most concentrated in polygodial. The correlation between content of polygodial with antifungal behavior of the different extracts, showed that LDCM of Autumn contains the highest content of polygodial and concomitantly the lowest MICs.

CONCLUSION

The ethnopharmacological use of Polygonum acuminatum aerial parts in the Argentinean traditional medicine for ailments related to fungal infections is supported by the results obtained in this investigation. From the obtained results, LDCM of Autumn, possessing the highest content of polygodial and the lowest MICs, appeared to be the most suitable extract for being used as antifungal in the traditional medicine. Nevertheless, if some other plant collection of another season different from Autumn is available, a LDCM extract would be the better option, because it contains a higher amount of polygodial compared to LHex, LEtOAc or LMeOH and therefore, a better antifungal activity can be expected.