Essential Oil of Cestrum diurnum L.: GC/MS Analysis, in Vitro and in Silico Anti-HCoV-229E Effects and Inhibitory Activity against LPS-Induced Inflammation.

Cestrum diurnum L. (Solanaceae) is a fragrant ornamental tree cultivated in different parts around the world. In this study, the essential oil (EO) of the aerial parts was extracted by hydrodistillation (HD), steam distillation (SD) and microwave-assisted hydro-distillation (MAHD). GC/MS analysis of the three EOs revealed that phytol represents the major component in SD-EO and MAHD-EO (40.84 and 40.04 %, respectively); while in HD-EO it only represented 15.36 %. The SD-EO showed a strong antiviral activity against HCoV-229E with IC50 of 10.93 µg/mL, whereas, MAHD-EO and HD-EO showed a moderate activity with IC50 values of 119.9 and 148.2 µg/mL, respectively. The molecular docking of EO major components: phytol, octadecyl acetate and tricosane showed a strong binding to coronavirus 3-CL (pro). Moreover, the three EOs (50 µg/mL) decreased the levels of NO, IL-6 and TNF-α and suppressed IL-6 and TNF-α gene expression in LPS-induced inflammation model in RAW264.7 macrophage cell lines.

Production and bioprocessing of camptothecin from Aspergillus terreus, an endophyte of Cestrum parqui, restoring their biosynthetic potency by Citrus limonum peel extracts.

The metabolic potency of fungi as camptothecin producer elevates their prospective use as an industrial platform for commercial production, however, the loss of camptothecin productivity by fungi with the storage and subculturing are the major obstacle. Thus, screening for endophytic fungal isolates inhabiting ethnopharmacological plants with an obvious metabolic stability and sustainability for camptothecin biosynthesis could be one of the most feasible paradigms. Aspergillus terreus ON908494.1, an endophyte of Cestrum parqui was morphologically and molecularly verified, displaying the most potent camptothecin biosynthetic potency. The chemical identity of A. terreus camptothecin was confirmed from the HPLC, FTIR and LC-MS/MS analyses, gave the same molecular structure and mass fragmentation patterns of authentic one. The purified putative camptothecin displayed a strong anticancer activity towards HepG-2 and MCF-7 with IC50 values 0.96 and 1.4 µM, respectively, with no toxicity to OEC normal cells. As well as, the purified camptothecin displayed a significant antifungal activity towards fungal human pathogen Candida albicans, Aspergillus flavus, and A. parasiticus, ensuring the unique structural activity relationships of A. terreus camptothecin, as a powerful dually active anticancer and antimicrobial agent. The camptothecin productivity of A. terreus was maximized by bioprocessing with Plackett-Burman design, with an overall 1.5 folds increment (170.5 µg/L), comparing to control culture. So, the optimal medium components for maximum yield of camptothecin by A. terreus was acid why (2.0 mL/L), Diaion HP20 (2.0 g/L), Amberlite XAD (2.0 g/L), dextrin (5.0 g/L), glucose (10.0 g/L), salicylic acid (2.0 g/L), serine (4.0 g/L), cysteine (4.0 g/L) and glutamate (10.0 g/L), at pH 6 for 15 days incubation. By the 5th generation of A. terreus, the camptothecin yield was reduced by 60%, comparing to zero culture. Interestingly, the productivity of camptothecin by A. terreus has been completely restored and over increased (210 µg/L), comparing to the 3rd generation A. terreus (90 µg/L) upon addition of methanolic extracts of Citrus limonum peels, revealing the presence of some chemical signals that triggers the camptothecin biosynthetic machinery. The feasibility of complete restoring of camptothecin biosynthetic-machinery of A. terreus for stable and sustainable production of camptothecin, pave the way for using this fungal isolate as new platform for scaling-up the camptothecin production.

Sensing of mercury ion using light induced aqueous leaf extract mediated green synthesized silver nanoparticles of Cestrum nocturnum L.

In this study, a simple, one-pot, and eco-friendly biosynthesis of silver nanoparticles (AgNPs) was accomplished with the use of aqueous leaves extract of Cestrum nocturnum L.(AECN). Different techniques like ultraviolet-visible (UV-Vis) spectrophotometry, Fourier transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning area electron diffraction were used to investigate the optical, operational, and physical properties of the green synthesized AECN-AgNPs.The AECN-AgNPs were further used for the detection of Hg2+ by UV-Vis and electrochemical methods. The disintegration of the AECN-AgNPs solution caused the formation of an Ag-Hg amalgam, which caused discoloration of the solution. Sensing performance for a variety of metals such as Na+, K+, Mg2+, Ca2+, Ni2+, Cu 2+, Fe3+, Zn2+, Co2+, Cd2+, Pb2+, As3+, and Mn2+ at 10-mM concentrations was measured in order to determine the selectivity of the sensor towards the Hg2+. For the electrochemical determination of 2 + Hg2+ , AECN-AgNPs were immobilized on a glassy carbon (GC) electrode, and the resulting modified electrode (GC/AECN-AgNPs) was characterized by cyclic voltammetry. This phenomenon is advantageously used for the sensitive determination of trace level Hg2+. GC/AECN-AgNPs demonstrated a linear calibration range of 100 nM to 10 µM and a limit of detection of 21 nM for Hg2+ determination.

Green Synthesized Zinc Oxide Nanoparticles Based on Cestrum diurnum L. of Potential Antiviral Activity against Human Corona 229-E Virus.

SARS-CoV-2 has caused more than 596 million infections and 6 million fatalities globally. Looking for urgent medication for prevention, treatment, and rehabilitation is obligatory. Plant extracts and green synthesized nanoparticles have numerous biological activities, including antiviral activity. HPLC analysis of C. dirnum L. leaf extract showed that catechin, ferulic acid, chlorogenic acid, and syringic acid were the most major compounds, with concentrations of 1425.16, 1004.68, 207.46, and 158.95 µg/g, respectively. Zinc nanoparticles were biosynthesized using zinc acetate and C. dirnum extract. TEM analysis revealed that the particle size of ZnO-NPs varied between 3.406 and 4.857 nm. An XRD study showed the existence of hexagonal crystals of ZnO-NPs with an average size of 12.11 nm. Both ZnO-NPs (IC50 = 7.01 and CC50 = 145.77) and C. dirnum L. extract (IC50 = 61.15 and CC50 = 145.87 µg/mL) showed antiviral activity against HCOV-229E, but their combination (IC50 = 2.41 and CC50 = 179.23) showed higher activity than both. Molecular docking was used to investigate the affinity of some metabolites against the HCOV-229E main protease. Chlorogenic acid, solanidine, and catchin showed high affinity (-7.13, -6.95, and -6.52), compared to the ligand MDP (-5.66 Kcal/mol). Cestrum dinurum extract and ZnO-NPs combination should be subjected to further studies to be used as an antiviral drug.

Biosystematic studies of some Egyptian species of Cestrum (Solanaceae).

Cestrum is the second largest genus of family Solanaceae, after Solanum, distributed in warm to subtropical regions. Species of genus Cestrum are one of the most ethnopharmacological relevant plants, for their broad biological and pharmacological properties. There is a scarcity to taxonomical studies and identification of these plants in Egypt, thus, the objective of this study was to implement various morphological features, chemical markers and molecular tools to emphasize the taxonomical features of the different Cestrum species. Morphologically, the epidermal cells of C. diurnum, C. elegans and C. parqui were irregular with sinuate anticlinal wall patterns for both surfaces, while, C. nocturnum has anticlinal walls, sinuolate with polygonal to irregular epidermal cells on the abaxial surface. The species of Cestrum have hypostomatic leaves, except C. parqui that has amphistomatic leaves. The experimented species of Cestrum have Anomocytic and anisocytic stomata, while, C. elegans has a diacytic stomata. The morphologically identified Cestrum spp were molecular confirmed based on their ITS sequences, the sequences of C. diurnum, C. nocturnum, C. elegans and C. parqui were deposited on genbank with accession # MT742788.1, MT749390.1, MW091481.1 and MW023744.1, respectively. From the SCOT analyses, the four species of Cestrum were grouped into 2 clusters (I, II), cluster I contains C. elegans, C. nocturnum and C. parqui, while cluster II contains only C. diurnum with 100% polymorphism for all primers. From the GC-MS profile, the C. diurnum exhibited a diverse metabolic paradigm, ensuring their richness with different metabolites comparing to other experimented Cestrum species. Among the total resolved metabolites, 15-methyltricyclo 6.5.2-pentadeca-1,3,5,7,9, 11,13-heptene was the highly incident compound in C. elegans (35.89%) followed by C. parqui (21.81%) and C. diurnum (11.28%), while it absent on C. nocturnum. The compound, 2,2',6,6'-tetra-tert-butyl-4,4'-methylenediphenol was highly detected in C. elegans and C. dirunum with minor amounts in the other Cestrum species. Cypermethrin and 3-butynyl-2,2,5-trimethyl-1,3-dioxane-5-methanol were pivotally reported in C. nocturnum. Taken together, from molecular and metabolic markers, C. diurnum, C. parqui and C. elegans have higher proximity unlike to C. nocturnum.

In vitro anticancer and antioxidant potential of Cestrum species.

The methanolic extract of leaves and stem of Cestrum nocturnum and Cestrum diurnum were investigated for their antioxidant and anticancer attribute through standard methods. 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay was carried out to estimate the antioxidant activity of the extracts. Whereas, anticancer potential of extracts were tested against colon cancer cell line, HCT 116 and acute myeloid leukemia (AML) cell lines, THP-1. Results showed that extracts of both plants exhibited a very strong antioxidant activity in a dose dependent manner. In addition, both extracts efficiently increased the cell death in two different cancer cell lines. Moreover, DNA fragmentation analysis further strengthens the anticancer potential of extracts of both types of plants. Current study, therefore, provide a preliminary data highlighting the antioxidant and anticancer activities of methanolic extract of leaves and stem of Cestrum nocturnum and Cestrum diurnum.

Hypolipidemic effect of steroid compound from Cestrum diurnum (Solanaceae: Solanales) in normocholesterolemic albino rat.

The present study was carried out to establish the hypolipidemic effect of a phyto-steroid compound isolated from the chloroform: methanol extract of fresh mature leaves of the plant Cestrum diurnum (Solanaceae: Solanales). Change in the haematological parameters was studied in normocholesterolemic albino rats after oral administration of single dose of isolated phytosteroid (2 mg/ day) up to 15 days and compared with control rats. Application of phytosteroid fraction resulted in a significant reduction in total plasma cholesterol and free cholesterol levels. The plasma triglyceride levels also decreased significantly. A sharp increase in the HDL cholesterol level and a significant decrease in the LDL and VLDL amount were also documented. Free fatty acid level was significantly low in treated rats.

Usos y costumbres sobre hierbas medicinales en barrios periurbanos del sudeste de la ciudad de Salta, Argentina / Uses and customs on medicinal herbs in periurban neighborhoods ofsoutheastern Salta City, Argentina

Desde la medicina oficial se desconoce y subestima el uso de otras formas de atención, por lo que este trabajo tiene como objetivos caracterizar el conocimiento sobre uso de hierbas medicinales en la zona sudeste de la ciudad de Salta; identificar cuáles se utilizan para tratar problemas de salud; y valorar su frecuencia de uso. Se realizó una investigación cuali-cuantitativa, entrevistando a informantes claves y grupos focales. Se confeccionaron listas de hierbas medicinales, y sus usos se categorizaron por problemas de salud. Se realizó una encuesta sobre frecuencia de usos medicinales. Se mencionaron 59 hierbas medicinales con una media de 2,3 usos por planta. Con un "Nivel de importancia Significativo" se encuentran quimpe, tusca, paico, coca, molle, ruda y hediondilla. El "coqueo" se encontró en 54% de las familias. El 52% utiliza alguna hierba para afecciones gastrointestinales, el 45% para problemas de la piel, el 40 % para afecciones respiratorias, el 33% para "empacho" y 17% para problemas renales, sin diferencias significativas en los usos por grupo etáreo. La población tiene amplio conocimiento sobre hierbas medicinales. La medicina formal debe legitimar estos conocimientos e incluirlos en su práctica.

Traditional health professionals underestimate and fail to recognize the use of other forms of health care, therefore this research has the objective of characterizing knowledge about the use of medicinal herbs in the southeastern area of Salta city; to identify which herbs are used to treat health problems; and to assess its frequency of use. Qualitative and quantitative research was conducted by interviewing key informants and focus groups. Lists of medicinal herbs and uses were created and categorized by health problems. Finally, a closed survey on frequency of use was carried out. Fifty-nine herbs were mentioned with an average of 2.3 uses per plant. quimpe, tusca , paico, coca, molle, ruda and hediondillawere herbs marked as “with a Significant Level of Impotanse”. The use of coca was found in 54% of the families interviewed. Fifty-two percent used some herb for gastrointestinal disorders, 45% for skin problems, 40% for respiratory conditions, 33% for indigestion and 17% for kidney problems, with no significant differences in uses according toage groups. Population has a good knowledge of medicinal herbs. Formal medicine should legitimize this knowledge and include it in its practice.

Antifungal Saponins from the Maya Medicinal Plant Cestrum schlechtendahlii G. Don (Solanaceae).

Bioassay-guided fractionation of the crude extract (80% EtOH) of the leaves of Cestrum schlechtendahlii, a plant used by Q'eqchi' Maya healers for treatment of athlete's foot, resulted in the isolation and identification of two spirostanol saponins (1 and 2). Structure elucidation by MS, 1D-NMR, and 2D-NMR spectroscopic methods identified them to be the known saponin (25R)-1ß,2α-dihydroxy-5α-spirostan-3-ß-yl-O-α-L-rhamnopyranosyl-(1 → 2)-ß-D-galactopyranoside (1) and new saponin (25R)-1ß,2α-dihydroxy-5α-spirostan-3-ß-yl-O-ß-D-galactopyranoside (2). While 2 showed little or no antifungal activity at the highest concentration tested, 1 inhibited growth of Saccharomyces cerevisiae (minimum inhibitory concentration (MIC) of 15-25 µM), Candida albicans, Cryptococcus neoformans, and Fusarium graminearum (MIC of 132-198 µM).

Caracterización de extractos hidroalcohólico y acuoso de Cestrum parqui L'Herit (palqui) respecto de su actividad antioxidante y surfactante / Characterization of hydroalcoholic and aqueous extracts of Cestrum parqui L'Herit (palqui) with respect to its antioxidant and surfactant activity

Cestrum parqui L'Herit (n.v. palqui) es una planta originaria de Sudamérica cuyos efectos benéficos descritos incluyen acción antipirética y sudorífica, tratamiento de diversas afecciones a la piel como quemaduras, eczema, impétigo y herpes. Hasta hoy, sólo se ha podido establecer científicamente su efecto antiinflamatorio y un discreto efecto antipirético. Sin embargo, se han descrito intoxicaciones agudas en bovinos y ovinos asociadas al consumo de palqui. Los efectos tóxicos incluyen necrosis hepática severa y hemorragia generalizada en los animales. Los estudios científicos relacionados con los efectos benéficos y tóxicos de esta planta son escasos. Es por ello, que en este trabajo se caracterizaron dos extractos, uno hidroalcohólico y el otro acuoso, de hojas y tallos de la parte aérea de Cestrum parqui L'Herit respecto de su capacidad antioxidante y surfactante. Ambos extractos previnieron en distinta magnitud, la oxidación de los lípidos y los tioles proteicos microsómicos, fenómenos inducidos por el sistema Fe3+/ascorbato. El extracto hidroalcohólico resultó ser el mejor antioxidante, aunque su concentración de polifenoles fue 4,2 veces menor que la del extracto acuoso. Asimismo, el extracto hidroalcohólico fue 8,5 veces más potente en causar la liberación de hemoglobina eritrocitaria, por lo tanto, el de mayor actividad surfactante. Estos resultados indicarían que las diferencias en las actividades estudiadas dependen no sólo de la concentración de antioxidantes, sino además, de otras variables. Así, la calidad y cantidad de los principios activos extraídos desde la droga vegetal dependen principalmente del solvente utilizado. Al final del manuscrito, los resultados se discuten desde el punto de vista farmacológico

[Sperm immobilizing effect of leaves extracts of Cestrum parqui]. / Effet immobilisant des spermatozoïdes par les extraits des feuilles du Cestrum parqui.

OBJECTIVE: The leaves extracts of Cestrum parqui were reported to have spermicidal activity. The current investigation identified the spermicidal component of the extracts and evaluated its spermicidal potential in vitro, particularly the effects on sperm motility and vitality. METHODS: Sperms were prepared by discontinuous buoyant density gradient centrifugation and incubated with varying concentrations of extract from C. parqui (40-250 µg/ml) at 37°C and 5% CO(2). The mode of spermicidal action was evaluated by sperm motility and vitality at different intervals ranging from 5 to 240 minutes. Morphological changes in human spermatozoa after exposure to the extract were evaluated under transmission electron microscope. RESULTS: A dose- and time-dependent effect of this extract on sperm motility and viability was observed. The mean effective concentration of extracts that induced irreversible immobilization was 250 µg/ml. Transmission electron microscope revealed a significant damage to sperm membrane in head and acrosomal membranes, notable swelling and disruption. CONCLUSION: Our study indicates that this natural extract has potential spermicidal effect in vitro. It can adequately replace nonoxynol-9 in vaginal contraceptives to make them more vaginally safe and ecofriendly.

Bioefficacy of Plumbago zeylanica (Plumbaginaceae) and Cestrum nocturnum (Solanaceae) plant extracts against Aedes aegypti (Diptera: Culicide) and nontarget fish Poecilia reticulata.

In a search for natural products that could be used to control the vectors of tropical diseases, extracts of medicinal plants Plumbago zeylanica and Cestrum nocturnum have been tested for larvicidal activity against second, third, and fourth instar larvae of Aedes aegypti. The LC(50) values of all the extracts in different solvents of both the plants were less than 50 ppm (15.40-38.50 ppm) against all tested larval instars. Plant extracts also affected the life cycle of A. aegypti by inhibition of pupal development and adult emergence with increasing concentrations. The larvicidal stability of the extracts at five constant temperatures (19°C, 22°C, 25°C, 28°C, and 31°C) evaluated against fourth instar larvae revealed that toxicity of both plant extracts increases with increase in temperature. Toxicity studies carried out against fish species Poecilia reticulata, the most common nontarget organism in the habitats of A. aegypti, showed almost nil to meager toxicity at LC(50) and LC(90) doses of the plant extracts. The qualitative analysis of crude extracts of P. Zeylanica and C. nocturnum revealed the presence of bioactive phytochemicals with predominance of plumbagin in P. zeylanica and saponins in C. nocturnum. Partially purified plumbagin from P. zeylanica and saponins from C. nocturnum were obtained, and their presence was confirmed by thin-layer chromatography and biochemical tests. The bioassay experiment of partially purified secondary metabolites showed potent mosquito larvicidal activity against the fourth instar larval form. Therefore, this study explored the safer and effective potential of plant extracts against vector responsible for diseases of public health importance.

Steroidal saponins from the fruits of Cestrum ruizteranianum.

Seven spirostane and furostane-type glycosides were isolated from the aqueous methanolic extract of the fruits of Cestrum ruizteranianum and characterized mainly by 2D NMR spectroscopy and mass spectrometry. These known saponins belong to the delta5-spirostene and delta5-furostene series and are reported in this species for the first time.

Modulation of CD86 expression in skin dendritic cells does not always correlate with changes in DC motility, migration and allostimulatory functions.

CD86 expression is a well-known activation marker of dendritic cells (DC). In this study, we compared the level of CD86 expression in monocyte-derived skin DC with their motility, migratory abilities and allostimulatory capabilities. We show that motility and migration could be uncoupled from activation and that the immune response-modulating effects of certain compounds may correlate with down-regulation of CD86 expression rather than with effects on motility and migration.

Anti-inflammatory and analgesic components from "hierba santa," a traditional medicine in Peru.

"Hierba santa," a Peruvian herbal medicine, is used to alleviate many symptoms, including headache, hemorrhoids, fever, and rheumatism. Several Cestrum species are said to be the origin of hierba santa. Three lots of hierba santa: Cestrum auriculatum (herb 1 and herb 2) and C. hediundinum (herb 3), which were purchased from Peruvian markets at Cuzco (Andes area) and Equitos (Amazon area), respectively, were examined for their pharmacological activities and active components. Herbs 1-3 showed anti-inflammatory and analgesic activities in the in vivo writhing inhibition test in mouse and inhibited prostaglandin E(1)-, E(2)-, or ACh-induced contractions of guinea pig ileum in the Magnus method. Activity-based separation of each extract yielded cestrumines A and B, cestrusides A and B, a mixture of (+)- and (-)-pinoresinol glucosides, nicotiflorin, rutin, sinapoyl glucose, ursolic acid, beta-sitosteryl glucoside, and 2-sec-butyl-4,6-dihydroxyphenyl-beta-D: -glucopyranoside. Among them, cestrumine A and cestrusides A and B are new compounds. All three lots of hierba santa do not contain exactly the same active components.

Cesdiurins I-III, steroidal saponins from Cestrum diurnum L.

Phytochemical investigation of a methanolic extract of leaves of Cestrum diurnum L (Solanaceae) resulted in isolation of several furostanol steroidal saponins, named cesdiurins I-III (1-3). Their structures of the isolated compounds were determined by spectroscopic analyses, including by use of 1D and 2D NMR spectroscopic techniques as well as by mass spectral analyses.

Laboratory evaluation of a phytosteroid compound of mature leaves of Day Jasmine (Solanaceae: Solanales) against larvae of Culex quinquefasciatus (Diptera: Culicidae) and nontarget organisms.

Crude mature leaves extract of Day Jasmine, Cestrum diurnum (Solanaceae: Solanales), was investigated for larvicidal activities against Culex quinquefasciatus, the vector of human filariasis. All the graded concentrations (0.1%, 0.2%, 0.5%, 1%, 1.5%, 2%, 2.5%, and 3% v/v) showed significant (P < 0.05) larval mortality, and results of regression equations revealed that the mortality rates were positively correlated with the concentrations of the extract (R (2) close to 1). LC(50), LC(95), and LC(99) values were calculated at different time intervals, and the lowest value was recorded at the 72-h bioassay for third-instar larvae. Significant changes in the larval mortality (F < 0.05) was also recorded between the periods of exposure and between instars during t test and single analysis of variance analysis. No mortality was noticed for nontarget organisms, such as Oreochromis niloticus niloticus and Chironomid larvae within 72 h of postexposure to 1%, 2%, and 3% crude plant extract under the laboratory condition. Qualitative and chromatographic analysis of the crude extract of C. diurnum revealed the presence of many bioactive phytochemicals. The bioassay experiment with the third-instar larval form established that the presence of a steroid compound (R (f), 0.67) was responsible for mosquitocidal activity.

Behavioral and antiepileptic effects of acute administration of the extract of the plant Cestrum nocturnum Lin (lady of the night).

Cestrum nocturnum is a garden shrub from the family Solanaceae and is used as a remedy for different health disorders. The aim of the present work was to investigate the potential neuropharmacological action profile of decoctions obtained from dry leaves of the plant. Decoctions were tested in different neuropharmacological models-Irwin test, exploratory behavior, tests for analgesia, isoniazid- and picrotoxin-induced convulsions, and maximal electroshock seizures-in mice, as well as in amphetamine-induced stereotypies and penicillin epileptic foci in rats. Decoctions of 1 and 5% (D1 and D5) induced restlessness, and the 30% decoction (D30) induced passivity. D5 and D30 reduced significantly exploratory behavior and amphetamine-induced stereotypies within a 3-hour observation period. The latter effect was apparent during the second 60 minutes. Decoctions reduced the amount of writhes induced by acetic acid in a dose-dependent manner, but were not effective in the hot plate model. The decoctions were not effective against pharmacologically induced convulsions. However, repeated administration of five doses of D5, at 1-hour intervals, reduced the amplitude of penicillin-induced epileptic spikes in both primary and secondary foci, in curarized rats. Taken together, the results suggest that C. nocturnum possesses active substances with analgesic activity provided through a peripheral action mechanism, in parallel with some psychoactive activity that does not fit well the neuropharmacological action profile of known reference neurotropic drugs.

Differential effects of NAA and 2,4-D in reducing floret abscission in cestrum (Cestrum elegans) cut flowers are associated with their differential activation of Aux/IAA homologous genes.

BACKGROUND AND AIMS: A previous study showed that the relative effectiveness of 2,4-dichlorophenoxyacetic acid (2,4-D) compared with that of 1-naphthaleneacetic acid (NAA) in reducing floret bud abscission in cestrum (Cestrum elegans) cut flowers was due to its acropetal transport. The aim of the present study was to examine if the differential effect of these auxins on floret abscission is reflected in the expression of Aux/IAA genes in the floret abscission zone (AZ). METHODS: cDNAs were isolated by PCR-based cloning from the floret AZ of auxin-treated cut flowers. The expression patterns of the cDNAs in various tissues and the effect of indole-3-acetic acid (IAA), applied with or without cycloheximide, on their expression in the floret AZ were examined by northern blot analysis. The regulation of transcript accumulation in the floret AZ in response to NAA or 2,4-D was measured by real-time PCR during auxin pulsing of cut flowers and vase life, concomitantly with floret abscission. KEY RESULTS: Six isolated cDNAs were identified to represent Aux/IAA homologous genes, designated as Cestrum elegans (Ce)-IAA1 to Ce-IAA6. Four Ce-IAA genes were characterized as early auxin-responsive genes (ARGs), and two (Ce-IAA1 and Ce-IAA5) as late ARGs. Only Ce-IAA5 was AZ-specific in floret buds. A temporal regulation of Ce-IAA transcript levels in the floret AZ was found, with 2,4-D inducing higher expression levels than NAA in floret buds. These Ce-IAA expression levels were negatively correlated with floret abscission. CONCLUSIONS: The differential transport characteristics of NAA and 2,4-D in cestrum cut flowers were reflected in differential activation of the Ce-IAA genes identified in the floret AZ. Therefore, Aux/IAA genes can be used as molecular markers to measure auxin activity, which reflects free auxin level in the AZ. Two of the identified genes, Ce-IAA1 and Ce-IAA5, may also have a regulatory role in abscission.