Ten essential oils, namely, mint (Mentha spicata L.,Lamiaceae), ginger (Zingiber officinaleRosc.,Zingiberaceae), lemon (Citrus limon Burm.f.,Rutaceae), grapefruit (Citrus paradisi Macf., Rutaceae), jasmine (Jasminum grandiflora L.,Oleaceae), lavender (Mill.,Lamiaceae), chamomile (Matricaria chamomilla L., Compositae), thyme (Thymus vulgaris L., Lamiaceae), rose (Rosa damascena Mill.,Rosaceae) and cinnamon (Cinnamomum zeylanicumN. Lauraceae) were tested for their antibacterial activities towards Propionibacterium acnes and in vitro toxicology against three human cancer cell lines. Thyme, cinnamon and rose essential oils exhibited the best antibacterial activities towards P. acnes, with inhibition diameters of 40 ± 1.2 mm, 33.5 ± 1.5 mm and 16.5 ± 0.7 mm, and minimal inhibitory concentrations of 0.016% (v/v), 0.016% (v/v) and 0.031% (v/v), respectively. Time-kill dynamic procedures showed that thyme, cinnamon, rose, and lavender essential oils exhibited the strongest bactericidal activities at a concentration of 0.25% (v/v), and P. acnes was completely killed after 5 min. The thyme essential oil exhibited the strongest cytotoxicity towards three human cancer cells. Its inhibition concentration 50% (IC₅₀) values on PC-3, A549 and MCF-7 tumor cell lines were 0.010% (v/v), 0.011% (v/v) and 0.030% (v/v), respectively. The cytotoxicity of 10 essential oils on human prostate carcinoma cell (PC-3) was significantly stronger than on human lung carcinoma (A549) and human breast cancer (MCF-7) cell lines.

Antioxidant activities of the aqueous and ethanol extracts of pigeonpea [Cajanus cajan (L.) Millsp.] leaves, as well as petroleum ether, ethyl acetate, n-butanol and water fractions and the four main compounds separated from the ethanol extract, i.e. cajaninstilbene acid (3-hydroxy-4-prenylmethoxystilbene-2-carboxylic acid), pinostrobin, vitexin and orientin, were examined by a DPPH radical-scavenging assay and a β-carotene-linoleic acid test. In the DPPH system, the antioxidant activity of the ethanol extracts was superior to that of the aqueous extracts, with IC₅₀ values were 242.01 and 404.91 µg/mL, respectively. Among the four fractions, the ethyl acetate one showed the highest scavenging activity, with an IC₅₀ value of 194.98 µg/mL. Cajaninstilbene acid (302.12 µg/mL) and orientin (316.21 µg/mL) showed more efficient radical-scavenging abilities than pinostrobin and vitexin. In the β-carotene-linoleic acid test, the inhibition ratio (%) of the ethyl acetate fraction (94.13%±3.41%) was found to be the highest, being almost equal to the inhibition capacity of the positive control BHT (93.89%±1.45%) at 4 mg/mL. Pinostrobin (>500 µg/mL) and vitexin (>500 µg/mL) showed insignificant antioxidant activities compared with cajaninstilbene (321.53 µg/mL) and orientin (444.61 µg/mL). In general, the ethyl acetate fraction of the ethanol extract showed greater activity than the main compounds in both systems, such results might be attributed to the synergistic effects of the components. The antioxidant activities of all the tested samples were concentration-dependent. Based on the results obtained, we can conclude that the pigeonpea leaf extracts may be valuable natural antioxidant sources and are potentially applicable in both medicine and the healthy food industry.

Summary: For non‐model plants, functional characterization of genes is still hampered by lack of efficient stable transformation procedures. Here, we report a simple, fast and efficient transformation technique with Agrobacterium rhizogenes for generating stable transgenic roots in living plants to facilitate functional studies in vivo. We showed that injection of A. rhizogenes into stems of various plant species lead to stable transgenic root generation, which can sustain plant growth after the original, non‐transgenic roots were cut off. A transformation system was established for pigeon pea, a major woody food crop, after optimizing the selection of A. rhizogenes strains, bacterium concentration, injection position and seedling age. RT‐PCR and fluorescence observation indicated a transgenic root induction efficiency of about 39% in pigeon pea. Furthermore, induction of hairy roots was achieved in nine out of twelve tested economically important plants at an efficiency of 15–39%. As proof of concept, bimolecular fluorescence complementation (BiFC) assay was applied to test the interaction between CcCIPK14 and CcCBL1/2 in pigeon pea. Additionally, ectopic expression of the bZIP transcription factor MdHY5 from apple confirmed the utility of the transformation technique for engineering anthocyanin synthesis in roots. Taken together, we show that this method allows fast in vivo studies of gene function in a wide range of plant species.