Simultaneous Quantification of Two Flavonoids in Morus alba by High Performance Liquid Chromatography Coupled with Photodiode Array Detector

The root bark of Morus alba L. (Family: Moraceae) is an important medicinal herb in many countries and has long been used as a traditional medicine for the treatment of cough, fever, blood pressure reduction, and respiratory diseases. In the present study, the simultaneous determination of two flavonoids, kuwanon G and morusin, for quality control of M alba was conducted using high-performance liquid chromatography (HPLC) equipped with photodiode array (PDA) detector. The column used for separation of kuwanon G and morusin was a Gemini C18 analytical column maintained at 45°C. The mobile phase for efficient separation of two analytes was flowed 0.1% (v/v) aqueous formic acid-acetonitrile with gradient elution. The detection wavelength for quantification was set at 266 nm. The optimized method showed good linearity with coefficients of determination of 0.9998 within the tested concentration ranges. The limits of detection for the two flavonoids, kuwanon G and morusin, were 0.69 μg/mL and 0.35 μg/mL and the limits of quantification of kuwanon G and morusin, were 2.10 μ/mL and 1.07 μg/mL. The recoveries were 98.40–111.55% and the relative standard deviation (RSD) value was within 3.50%. The RSD values of intra- a g d interday precisions were 0.08–0.70% and 0.06-0.48%, respectively. The amounts of kuwanon G and morusin were 1.94-2.26 mg/g and 1.05–1.12 mg/g. The established HPLC-PDA method will help to improve the quality control of M. alba and related products.

Comparison of Different Strains of Agrobacterium rhizogenes for Hairy Root Induction and Betulin and Betulinic Acid Production in Morus alba

Three Agrobacterium rhizogenes strains were tested for their ability to transform the plant Morus alba L. and to induce production of the secondary metabolites betulin and betulinic acid. All the tested strains of A. rhizogenes (R1601, LBA9402 and R1000) were able to induce hairy root formation in leaf tissue explants. Strain LBA9402 had the highest rate of infection (92.7% ± 8.8%), whereas strain R1601 had the lowest rate (87.4% ± 9.3%). The highest number of hairy roots per explant (5.6 ± 0.5) and the greatest root length (2.4 ± 0.2 mm) were obtained with strain LBA9402. We also evaluated dry weight (a measure of growth) and betulin and betulinic acid production in hairy roots and found that the highest growth (167.8 ± 14.5 mg/flask) occurred after infection with strain LBA9402. Furthermore the highest production of betulin (5.4 ± 0.4 mg/g dry weight) and betulinic acid (2.3 ± 0.2 mg/g dry weight) was noted using strain LBA9402. Among three elicitors, yeast extract showed the highest induction of betulin production (8.7 ± 0.4 mg/g) and silver nitrate induced the highest yield of betulinic acid (4.1 ± 0.2 mg/g). Our study showed that A. rhizogenes strain LBA9402 was the most effective of the three tested strains for production of transformed root cultures and betulin and betulinic acid.

Essential Oils of Morus alba and M. nigra Leaves: Effect of Drying on the Chemical Composition

Detailed GC and GC/MS analyses of essential-oil samples obtained by hydrodistillation of Morus alba L. and M. nigra L. leaves (four samples) allowed the identification of 131 constituents representing 95.1 – 96.4% of the total GC peak areas. The most abundant compounds classes were alkanes, diterpenoids, carotenoid-derived compounds and fatty acid-related constituents with trans-phytol (7.9 – 71.2%), ( E,E)-geranyl linalool (0.2 – 8.0%), ( Z)-bovolide (8.1%) and n-chain alkanes (in total, 17.5 – 52.4%) as the major constituents of the analyzed samples. In general, there were only quantitative differences noted between M. nigra essential oils from fresh and dry leaves. The most discernable changes included a variation in the content of the major constituents (e.g. the relative amount of trans-phytol and the total amount of alkanes decreased by 5.8% and ≈ 2%, respectively, while that of ( E,E)-geranyl linalool increased by 7.8%). On the other hand, the composition of M. alba essential oil was much more significantly affected by the drying process. The highest quantitative differences were noted for trans-phytol, geranyl acetone, and all isomers of 4,6,8-megastigmatrien-3-one. Also, a rare plant metabolite, ( Z)-bovolide, characteristic of leaf senescence, was only identified (8.1%) in the essential oil of M. alba dried leaves.