Exotic tree and shrub invasions alter leaf-litter microflora and arthropod communities.

Approximately 90% of all annual net primary productivity in temperate deciduous forests ends up entering the detritus food web as leaf litter. Due to chemical and physical differences from native litter, inputs from invasive species may impact the litter-dwelling community and ecosystem processes. We compared leaf-litter nutritional quality and decomposition rates from two invasive shrubs, Lonicera maackii and Rhamnus davurica, and the invasive tree Ailanthus altissima to litter from native oak-hickory forest in the Shenandoah Valley of Virginia, USA. We sampled litter from both invaded and uninvaded habitats and conducted litter colonization experiments to test for effects on microflora and the litter-dwelling arthropod communities. Litter from all three invasive species decomposed more rapidly than native litter, with native habitats averaging two to nearly five times as much litter by June. Invasive litter had higher nitrogen concentration and lower C:N ratios than native litter. Invasive litter supported greater growth of bacteria and fungi. Higher numbers of arthropods colonized invasive litter than native litter, but litter arthropod numbers on the forest floor of invaded habitats dropped in the early summer as litter decomposed. Litter had no effect on arthropod richness. Over short time scales, our results indicate that these invasive species represent beneficial, novel resources for the litter-dwelling community. However, the short-lived nature of this resource resulted in a crash in the abundance of the litter-dwelling organisms once the litter decomposed. As a whole, native habitat seems to support a larger, more stable litter-dwelling community over the course of a growing season.

Screening for anti-proliferative and anti-inflammatory components from Rhamnus davurica Pall. using bio-affinity ultrafiltration with multiple drug targets.

Rhamnus davurica Pall. (R. davurica) has been used as a traditional medicine for many years in China and abroad and shown a wide spectrum of biological activities. Previously, we reported the phytochemical fingerprinting profile of R. davurica, its distinct anti-proliferative activities against HT-29 and SGC-7901 cell lines, and the topoisomerase I (Top I) ligands based on bio-affinity ultrafiltration and HPLC-MS (UF-HPLC-MS). Nevertheless, among the 32 peaks detected in the fingerprinting profile, the common bioactive constituents responsible for the anti-inflammatory and anti-proliferative activities in the extracts remain elusive. To further explore the specific responsible components for their diversified activities and their potential action targets/mechanisms, the method based on bio-affinity UF-HPLC-MS using therapeutic targets like Top I and cyclooxygenase 2 (COX-2) was established to rapidly screen and identify the ligands binding to these known target enzymes. As a result, 12 components were revealed as potential Top I ligands along with 11 components as potential COX-2 ligands, where several components were revealed to possess both activities. Further validations of these bioactive components have also been conducted and confirmed their highlighted activities. This integrated method of UF-HPLC-MS exhibits high efficiency in rapidly screening for multi-target bioactive components responsible for multiple pharmacological effects from the complex natural products and could be very useful to explain the complex action mechanisms of herb medicines in a complex multi-component and multi-target mode at the molecular level. Graphical abstract Schematic diagram of UF-HPLC-MS assay to screen for Top I and COX-2 ligands. The principle of the assay usually involves the following steps: incubation, ultrafiltration, and identification.

Screening for Natural Inhibitors of Topoisomerases I from Rhamnus davurica by Affinity Ultrafiltration and High-Performance Liquid Chromatography-Mass Spectrometry.

Topoisomerase I (Topo I) catalyzes topological interconversion of duplex DNA during DNA replication and transcription, and has been deemed as important antineoplastic targets. In this study, the fraction R.d-60 from ethyl acetate extracts of Rhamnus davurica showed higher inhibitory rates against SGC-7901 and HT-29 compared with the R.d-30 fraction in vitro. However, the specific active components of R.d-60 fraction remain elusive. To this end, a method based on bio-affinity ultrafiltration and high performance liquid chromatography/electrospray mass spectrometry (HPLC- ESI-MS/MS) was developed to rapidly screen and identify the Topo I inhibitors in this fraction. The enrichment factors (EFs) were calculated to evaluate the binding affinities between the bioactive constituents and Topo I. As a result, eight ligands were identified and six of which with higher EFs showed more potential antitumor activity. Furthermore, antiproliferative assays in vitro (IC50 values) with two representative candidates (apigenin, quercetin) against SGC-7901, HT-29 and Hep G2 cells were conducted and further validated. Finally, the structure-activity relationships revealed that flavones contain a C2-C3 double bond of C ring exhibited higher bio-affinities to Topo I than those without it. This integrated method combining Topo I ultrafiltration with HPLC-MS/MS proved to be very efficient in rapid screening and identification of potential Topo I inhibitors from the complex extracts of medicinal plants, and could be further explored as a valuable high-throughput screening platform in the early drug discovery stage.

Analysis of Flavonoids in Rhamnus davurica and Its Antiproliferative Activities.

Rhamnus davurica Pall. (R. davurica) has been used as a traditional medicinal herb for many years in China and abroad. It has been well documented as a rich source of flavonoids with diversified structures, which in turn results in far-ranging biological activities, such as anti-inflammation, anticancer, antibacterial and antioxidant activities. In order to further correlate their anticancer potentials with the phytochemical components, the fingerprint profile of R. davurica herb from Dongbei was firstly investigated using HPLC-ESI-MS/MS. Thirty two peaks were detected and identified, 14 of which were found in R. davurica for the first time in this work. Furthermore, a total of 23 peaks were resolved as flavonoids, which are the major components found in R. davurica. Meanwhile, the antiproliferative activities against human cancer cells of HT-29 and SGC-7901 in vitro exhibited distinct inhibitory effects with IC50 values at 24.96 ± 0.74 and 89.53 ± 4.11 µg/mL, respectively. Finally, the general toxicity against L-O2 cells displayed a much higher IC50 at 229.19 ± 8.52 µg/mL, which suggested very low or no toxicity on hepatic cell viability. The current study revealed for the first time the correlations between the flavonoids of R. davurica with their antiproliferative activities, which indicated that the fingerprint profile of flavonoids and their anticancer activities could provide valuable information on the quality control for herbal medicines and their derived natural remedies from this valuable medicinal plant.