Study of the Structure and Bioactivity of Polysaccharides from Different Parts of Stemona tuberosa Lour.

The polysaccharides from Stemona tuberosa Lour, a kind of plant used in Chinese herbal medicine, have various pharmacological activities, such as anti-inflammatory and antioxidant properties. However, the effects of the extraction methods and the activity of polysaccharides from different parts are still unknown. Therefore, this study aimed to evaluate the effects of different extraction methods on the yields, chemical compositions, and bioactivity of polysaccharides extracted from different parts of Stemona tuberosa Lour. Six polysaccharides were extracted from the leaves, roots, and stems of Stemona tuberosa Lour through the use of hot water (i.e., SPS-L1, SPS-R1, and SPS-S1) and an ultrasound-assisted method (i.e., SPS-L2, SPS-R2, and SPS-S2). The results showed that the physicochemical properties, structural properties, and biological activity of the polysaccharides varied with the extraction methods and parts. SPS-R1 and SPS-R2 had higher extraction yields and total sugar contents than those of the other SPSs (SPS-L1, SPS-L2, SPS-S1, and SPS-S2). SPS-L1 had favorable antioxidant activity and the ability to downregulate MUC5AC expression. An investigation of the anti-inflammatory properties showed that SPS-R1 and SPS-R2 had greater anti-inflammatory activities, while SPS-R2 demonstrated the strongest anti-inflammatory potential. The results of this study indicated that SPS-L1 and SPS-L2, which were extracted from non-medicinal parts, may serve as potent natural antioxidants, but further study is necessary to explore their potential applications in the treatment of diseases. The positive anti-inflammatory effects of SPS-R1 and SPS-R2 in the roots may be further exploited in drugs for the treatment of inflammation.

Semen-Like Floral Scents and Pollination Biology of a Sapromyophilous Plant Stemona japonica (Stemonaceae).

By emitting scent resembling that of organic material suitable for oviposition and/or consumption by flies, sapromyophilous flowers use these flies as pollinators. To date, intensive scent analyses of such flowers have been restricted to Apocynaceae, Annonaceae, and Araceae. Recent studies have suggested that the wide range of volatile organic compounds (VOCs) from sapromyophilous flowers play an important role in attracting saprophagous flies by mimicking different types of decomposing substrates (herbivore and carnivore feces, carrion, and the fruiting bodies of fungi, etc.). In this study, we report the flower visitors and the floral VOCs of Stemona japonica (Blume) Miquel, a species native to China. The flowers do not produce rewards, and pollinators were not observed consuming pollen, thus suggesting a deceptive pollination system. Headspace samples of the floral scent were collected via solid-phase micro-extraction and analysed by gas chromatography coupled with mass spectrometry. Main floral scent compounds were 1-pyrroline (59.2%), 2-methyl-1-butanol (27.2%), and 3-methyl-1-butanol (8.8%), and resulted in a semen-like odor of blooming flowers. The floral constituents of S. japonica were significantly different from those found in previous sapromyophilous plants. An olfaction test indicated that 1-pyrroline is responsible for the semen-like odor in S. japonica flowers. Main flower visitors were shoot flies of the genus Atherigona (Muscidae). Bioassays using a mixture of all identified floral volatiles revealed that the synthetic volatiles can attract Atherigona flies in natural habitats. Our results suggest that the foul-smelling flowers of S. japonica may represent a new type of sapromyophily through scent mimicry.

Absolute structures of stemona-lactam S and tuberostemospiroline, alkaloids from stemona tuberosa.

A new alkaloid, stemona-lactam S, and a known alkaloid, tuberostemospiroline, were isolated from the roots of Stemona tuberosa LOUR. (Stemonaceae). Their structures and absolute stereochemistry were established by X-ray crystallography and vibrational circular dichroism.

Green synthesis of silver and gold nanoparticles using Stemona tuberosa Lour and screening for their catalytic activity in the degradation of toxic chemicals.

In the present study, silver and gold nanoparticles (AgNPs and AuNPs) were green synthesised using the aqueous plant extract of Stemona tuberosa Lour. When plant extract was mixed with AgNO3 and HAuCl4 solutions in separate reactions, the amalgamated solutions turned deep reddish brown and dark purple in colour after 48 h indicating the formation of AgNPs and AuNPs. UV-Visible analysis of green synthesised AgNPs and AuNPs have shown absorption maximum at 443.85 nm and 539.72 respectively after 48 h. Energy dispersive X-ray spectroscopy (EDX) analysis confirmed the presence of pure silver in the green synthesised AgNPs and pure gold in the plant-mediated AuNPs. X-ray diffractometer (XRD) data revealed the face-centred cubic nature of AgNPs. Fluorescence transmission infrared (FTIR) spectrum has shown the characteristic peaks of different phytochemicals in the plant extract which acted as stabilising or capping agents of AgNPs. Scanning electron microscopy (SEM) analysis of AgNPs and AuNPs revealed that the nanoparticles are monodispersed. Transmission electron microscopy (TEM) studies revealed that AgNPs were mostly spherical with an average size of 25 nm whereas selected area electron diffraction (SAED) analysis confirmed their crystalline nature. Both AgNPs and AuNPs of S. tuberosa Lour have shown potential catalytic activity in the presence of sodium borohydride (NaBH4) in the degradation and removal of 4-nitrophenol, methylene blue, methyl orange and methyl red.

Pyrrolo- and pyridoazepine alkaloids as chemical markers in Stemona species.

Broad-based phytochemical investigations on 31 Stemona species and geographical provenances led to an overview concerning characteristic accumulation trends and the distribution of different Stemona alkaloids. Two major metabolic differences suggested a taxonomic segregation of the complex Stemona tuberosa group from the other species, and was supported by morphological characters. Whereas most of the Stemona species were characterised by protostemonine type alkaloids, the S. tuberosa group clearly deviated by accumulation trends towards tuberostemonine or croomine derived alkaloids belonging to two different skeletal types. Also of chemotaxonomic relevance was the structural divergence of protostemonine type alkaloids into pyrrolo- or pyridoazepine derivatives represented by stemofoline or oxystemokerrine, respectively, as major constituents. Their common occurrence in different provenances of S. curtisii, also deviating from the other species by various chromosome numbers, deserves special taxonomic attention. Species specific chemical markers were given by the unique accumulation of didehydrostemofoline (=asparagamine A) in S. collinsae and stemokerrine in S. kerrii. In contrast to previous reports, no bisdehydro derivatives with an aromatic pyrrole ring were detected supporting the hypothesis that these alkaloids are artifacts. A new stereoisomer of tuberostemonine was isolated and identified by spectroscopic methods.

Proteomic profiling of Stemona alkaloids production response to chitosan elicitor.

The study purposed to investigate the protein expression of Stemona alkaloids biosynthesis response to chitosan elicitor by 2D gel electrophoresis. The total proteins extraction of Stemona roots were performed for comparison with the control and chitosan treatments. It was found that 15 out of 150 protein spots exhibited different expression between control and chitosan culture treatment. The identified 15 protein spots were subjected to amino acid sequencing and two proteins appeared interesting for examining Stemona alkaloids biosynthesis. After treated with chitosan, glutathione S-transferase became down-regulated while heat shock protein up-regulated in relation to the control treatment. These proteins may play roles in alkaloids biosynthesis via plant defense metabolism from the presumptions that chitosan might weaken the detoxifying function of glutathione S-transferase, then, heat shock protein is probably produced to signal for tissue protection mechanism. Thus, Stemona alkaloids may be responsive to this stress.

Total synthesis of (±)-maistemonine and (±)-stemonamide.

The first total synthesis of polycyclic Stemona alkaloid maistemonine has been achieved. The efficient approach features a stereoselective intramolecular Schmidt reaction, a ketone-ester condensation, and a Reformatsky reaction. Additionally, another Stemona alkaloid stemonamide was divergently synthesized from a common intermediate.

Structural relationships, distribution and biological activities of stemona alkaloids.

Stemona alkaloids represent a unique class of natural products exclusively isolated from the monocotyledonous family Stemonaceae comprising three genera mainly distributed in southeast Asia. Structurally the alkaloids are characterised by a pyrrolo[1,2- a]azepine nucleus usually linked with two carbon chains mostly forming terminal lactone rings. Based on biosynthetic considerations and their various distribution the present review describes 82 Stemona alkaloids grouped into three skeletal types. Due to different carbon chains attached to C-9 of the pyrroloazepine nucleus they were classified into stichoneurine-, protostemonine- and croomine-type alkaloids. The genera Croomia and Stichoneuron only accumulate croomine or stichoneurine derivatives, respectively, whereas the genus Stemona produces all three types of alkaloids. However, species-specific accumulation trends towards certain structural types represent valuable chemosystematic criteria. Bioassays with larvae of Spodoptera littoralis exhibited very high insect toxicity for the roots of Stemona species containing certain protostemonine derivatives, especially didehydrostemofoline, whereas those with dominating stichoneurine or croomine derivatives showed low toxicity but sometimes remarkable repellence due to an accumulation of tuberostemonine. Tuberostemonine also showed effects on the motility of helminth worms and reduced the excitatory transmission at the crayfish neuromuscular junction. Significant antitussive activity was shown for the stereoisomeric neotuberostemonine in guinea-pig after cough induction by citric acid aerosol stimulation. Studies on structure-activity relationship with seven related compounds revealed that the saturated tricyclic pyrrolobenzazepine nucleus of tuberostemonines is the prerequisite for antitussive activity.