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A new lignan (1) was isolated from the flowers of Forsythia koreana along with one known lignan, 4,4′-di-O-β-D-glucosylpinoresinol (2). The molecular structures were determined using spectral methods. These compounds were isolated from F. koreana flowers for the first time.

Yellow-leafed cultivars usually do not grow as vigorous as their green-leafed counterparts, which affect their use in landscapes. To breed Forsythia cultivars with both yellow leaves and vigorous growth, crosses between F. ‘Courtaneur’ (♀) and Forsythia koreana ‘Suwon Gold’ (♂) were conducted, and 52 F1 hybrid progenies with different leaf colors (green, chartreuse, and yellow) were obtained. The progenies were categorized into three groups [Yellow Group (YG), Chartreuse Group (CG), and Green Group (GG)] based on leaf colors. The growth index (GI) and the number of branches and leaves of YG progenies were significantly lower at 2%, 35%, and 34% of GG progenies. As the leaves changed from green to chartreuse and to yellow, chlorophyll content, leaf thickness, and chlorophyll fluorescence parameters decreased and the chloroplast structures were disintegrated gradually, which influenced the leaf photosynthetic activity and led to weak growth. Compared with yellow-leafed progenies, the leaf chlorophyll content and leaf thickness of chartreuse-leafed progenies were significantly higher at 71% and 9%. The chloroplast structure of stroma lamella of chartreuse-leafed progenies was relatively intact. Carboxylation efficiency (CE), photochemical efficiency of PS II (Fv/Fm), and the number of branches and leaves of GG progenies were significantly higher than YG progenies; however, they have no significant difference with CG progenies. The results were promising for breeding new forsythia cultivars from moderate growth and chartreuse leaves.

A simple method to prepare a high-content rutin fraction from Forsythia koreana flowers (HRFK) is described. Rutin, isolated for the first time from the flowers, was identified from spectroscopic data including nuclear magnetic resonance, mass spectrometry, and infrared. As a result of HPLC quantitative analysis, the content of rutin was found to be 80.0 ± 0.02% in HRFK. Our previous study reported that F koreana MeOH extract (FK) significantly recovered alloxan-induced pancreatic islets in zebrafish. However, HRFK as well as rutin exhibited an enhanced anti-diabetic effect compared to FK in our latest experiments. In conclusion, HRFK, as well as rutin and FK, have potential as anti-diabetic agents.

Background Breast cancer is the most common malignant disease in women. The patients with advanced breast cancer develop metastasis to bone. Bone metastasis and skeletal-related events by breast cancer are frequently associated with the invasiveness of breast cancer cells and osteoclasts-mediated bone resorption. Forsythia koreana is used in oriental traditional medicine to treat asthma, atopy, and allergic diseases. The aim of this study was to evaluate the inhibitory effects of F. koreana extracts on the invasion of breast cancer cells and bone resorption by osteoclasts. Methods Cell viability was measured by an MTT assay and the migration and invasion of MDA-MB-231 cells were detected by a Boyden chamber assay. The formation of osteoclasts and pit was detected using tartrate-resistant acid phosphatase staining and calcium phosphate-coated plates, respectively. The activities of matrix metalloproteinases (MMPs) and cathepsin K were evaluated by gelatin zymography and a cathepsin K detection kit. Results The fruit and leaf extracts of F. koreana significantly inhibited the invasion of MDA-MB-231 cells at noncytotoxic concentrations. The fruit extract of F. koreana reduced the transforming growth factor β1-induced migration, invasion and MMPs activities of MDA-MB-231 cells. In addition, the fruit, branch, and leaf extracts of F. koreana also inhibited the receptor activator of nuclear factor kappa-B ligand-induced osteoclast formation and osteoclast-mediated bone-resorbing activity by reducing the activities of MMPs and cathepsin K. Conclusions The extracts of F. koreana may possess the potential to inhibit the breast cancer-induced bone destruction through blocking invasion of breast cancer cells, osteoclastogenesis, and the activity of mature osteoclasts.

Six lignans including two new lignans were obtained as the principal components of the Forsythia koreana flowers via silica gel (SiO2 ), octadecyl SiO2 (ODS) as well as Sephadex LH-20 column chromatography. In addition to two new lignans, named koreanaside A ((7R,8S,7'R,8'S)-7,7'-diepoxy-5'-hydroxy-3,3'-dimethoxylignan 4-O-β-d-glucopyranoside) and koreanaside B ((7R,8S,7'S,8'R)-7,9'-epoxy-9,5',7'-trihydroxy-3,3'-dimethoxylignan 4-O-β-d-glucopyranoside), four known lignans were identified to be (+)-phylligenin, (-)-epipinoresinol, pinoresinol, and tinosposide A. The structures and absolute configurations of koreanasides A and B were established by means of analysis of spectroscopic data (NMR, IR, FAB-MS, and CD), whereas the structures of known lignans were identified by comparison their NMR and MS values with those in the reported literature. Their chemical structures including configuration were established by means of analysis of spectroscopic data (NMR, IR, FAB-MS, and CD) but also comparison of their NMR and MS values with those in the reported literature. This is the first article for isolation of six lignans of F. koreana flowers. Koreanasides A and B showed high radical scavenging activity with oxygen radical absorbance capacity (ORAC) values of 0.97 ± 0.01 and 1.02 ± 0.01, respectively. Koreanaside A also prohibited expressing VCAM-1 in MOVAS cells with 80.5% at 25 mg/mL.

The Oleaceae is a family of medium size with 25 genera and about 600 species. With regard to chemical constituents, it has been quite extensively investigated. It is mainly characterized by the presence of iridoid glucosides and phenylethanoid derivatives in the form of esters and glycosides of tyrosol (p-hydroxyphenyl-ethanol) and in particular the closely related dopaol (3,4-dihydroxyphenyl-ethanol).Coumarins and lignan glucosides are also common in the family, but they appear to have a more limited distribution [1 – 2]. The fruits of Forsythia koreana Nakai (Oleaceae) are known to have diuretic and damp-heat clearing actions, and have been used for the treatment of dysuria, edema, urinary tract infection, and retention of fluid in oriental traditional medicine [3]. This plant is known to possess antibacterial, antiinflammatory, and diuretic activities [4]. However, the mechanisms of action of this plant are still unknown. We describe here the isolation and structure elucidation of two new compounds from the methanol extract of the dried fruits of F. koreana, β -(3,4-dihydroxyphenyl)ethyl-O-α-rhamnopyranosyl-(1→4)-2-O(E)-caffeoyl-α-arabinopyranoside (1) and (2R,3S)-3hydroxy-2-hydroxypropylpyrrolidine (2) together with six known compounds (3 – 8).

Centrifugal partition chromatography was applied to separate arctigenin and matairesinol from Forsythia koreana extract with a two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water (5:5:5:5 v/v). Using this method, arctigenin and matairesinol were successfully separated from partially purified F. koreana extracts in only one step. The purities of isolated compounds were determined to be over 90% by HPLC analysis.