Dicentrine Analogue-Induced G2/M Arrest and Apoptosis through Inhibition of Topoisomerase II Activity in Human Cancer Cells.[Pubmed: 26158522]

Lindera megaphylla has been traditionally used as an antineoplastic and wound healing remedy. We previously demonstrated the antitumor effects of D-dicentrine, a natural aporphine alkaloid from the root of L. megaphylla. To generate analogues, series of phenanthrene alkaloids from D-dicentrine were synthesized by degradation with ethyl chloroformate in pyridine, base hydrolysis, and N-alkylation. In this study, we demonstrated that one of the synthesized D-dicentrine analogues (here after designated as analogue 1) exhibited more potent cytotoxic effects than D-dicentrine in colon adenocarcinoma, hepatoma, leukemia, and epidermoid carcinoma cells. We performed cell cycle and apoptotic analysis by flow cytometry, an apoptotic DNA detection ELISA assay, and topoisomerase II activity by the kinetoplast DNA concatenation assay for studying their cytotoxic mechanisms. We found that both D-dicentrine and analogue 1 induced apoptosis and G2/M arrest in HL-60 leukemia cells. The percentage of apoptotic cells induced by analogue 1 was 4.5-fold higher than that induced by D-dicentrine as evident from measuring the amount of histone-bound DNA fragments. Moreover, we found that analogue 1 was 28-fold more potent than D-dicentrine for inhibition of topoisomerase II activity by the kinetoplast DNA concatenation assay. Our findings indicate that D-dicentrine analogue 1 is very promising as a potential antitumor agent for future study.

Pit membrane chemistry influences the magnitude of ion-mediated enhancement of xylem hydraulic conductance in four Lauraceae species.[Pubmed: 21389001]

The ion-mediated enhancement of xylem hydraulic conductivity in angiosperms is thought to be controlled by the pectin chemistry of intervessel pit membranes. However, there is little or no direct evidence on the ultrastructure and chemical nature of pit membranes in species that show an 'ionic effect'. The potential link between the magnitude of the ionic effect and pectin composition in intervessel pit membranes of four Lauraceae species (Laurus nobilis, Lindera megaphylla, Litsea sericea and Umbellularia californica) that show rather similar vessel and pit dimensions was studied using transmission electron microscopy (TEM). The TEM observations confirmed the presence of a pectic matrix associated with intervessel pit membranes, indicating that the relative abundance of acidic versus methylesterified pectins was closely related to the ionic effect. The two species examined with a high ionic effect ~20%, i.e. Laurus nobilis and Umbellularia californica) showed relatively high levels of acidic pectins, whereas methylesterified pectins were abundant in Lindera megaphylla and Litsea sericea, which showed a low ionic effect (~10%). Variation in the ionic effect is strongly associated with the chemical nature of pit membrane pectins in the species studied. Our findings support the current interpretation of the ionic effect due to dynamic swelling and shrinking behaviour of pit membrane pectins.

Anti-tumor effects of d-dicentrine from the root of Lindera megaphylla.[Pubmed: 9581516]

d-Dicentrine, a naturally occurring aporphine type isoquinoline alkaloid, isolated from the root of Lindera megaphylla Hemsl. (Lauraceae), was evaluated for its potential anti-cancer activity. We found d-dicentrine significantly inhibited the growth of human hepatoma cell line HuH-7 by delaying its doubling time in tissue culture. An in vitro colony forming assay showed that d-dicentrine decreased the colony formation efficiency in both hepatoma cell lines, HuH-7 and MS-G2, used in our study. Biosyntheses of the macromolecules DNA and RNA were also strongly inhibited. An MTT assay in 21 tumor cell lines also revealed that d-dicentrine was most cytotoxic to esophageal carcinoma HCE-6, lymphoma cell lines Molt-4 and CESS, leukemia cell lines HL60 and K562, and hepatoma cell line MS-G2. An in vitro tumor growing assay in the Severe Combined immunodeficiency (SCID) mice showed that intraperitoneal injection of d-dicentrine at the dose of 100 micrograms twice a week for 4 weeks significantly inhibited the tumor incidence of leukemia cell line K562 in SCID mice. All these data indicated that d-dicentrine has potential anti-tumor applications.

Effects of dicentrine on the mechanical properties of systemic arterial trees in dogs.[Pubmed: 7564359]

We evaluated the effects of dicentrine on the physical properties of systemic arterial trees. Dicentrine, isolated from Lindera megaphylla, was identified as a potent, selective alpha 1-adrenoceptor antagonist. We used high-fidelity multisensor catheter to measure the ascending aortic pressure and flow signals in 9 mongrel dogs. A succinct T-tube model with vascular nonuniformity was adopted to relate the pulsatile pressure and flow waves. The model-estimated parameters were capable of representing the mechanical properties of the blood vessel walls. Dicentrine had a beneficial effect on the rigidity of head and body circulation, respectively. There were great improvements not only in the tube distensibility and wave transmission time, but also in the peripheral load compliance and resistance. In global circulation that was defined as the parallel combination of head and body circulation, dicentrine significantly reduced values in characteristic impedance of the ascending aorta from 164 +/- 67 to 105 +/- 43 dynes/s/cm5, and in wave reflection factor from 0.46 +/- 0.14 to 0.36 +/- 0.13, and in total peripheral vascular resistance from 4,751 +/- 1,226 to 3,581 +/- 1,277 dynes/s/cm5. On the other hand, total peripheral load compliance was increased from 0.2950 +/- 0.1794 to 0.4457 +/- 0.2199 ml/mm Hg. Cardiac output (CO) and heart rate (HR) remained unchanged, however. Dicentrine had an impact on the mechanical properties of Windkessel vessels and resistance vessels in the systemic circulation.

The electrophysiological effects of dicentrine on the conduction system of rabbit heart.[Pubmed: 7812635]

1. The electrophysiological effects of dicentrine, an aporphine alkaloid isolated from the root of Lindera megaphylla, were examined in the Langendorff perfused rabbit heart and rabbit isolated cardiac cells. 2. Standard electrophysiological characters were measured in the Langendorff perfused rabbit heart (control study) and after 5 min exposure to 1, 3 and 9 microM of dicentrine and during the subsequent recovery phase sequentially (n = 7). The same study protocols were performed in 0.5 to 4.5 microM quinidine (n = 7), 18 to 162 microM procainamide and N-acetylprocainamide (n = 7) for comparison. 3. The results showed that the spontaneously beating heart rate and the sinoatrial (SA) and atrioventricular nodal (AH) conduction time were not significantly affected by dicentrine but were significantly suppressed by the higher doses of quinidine (4.5 microM) and procainamide (162 microM). 4. The His-Purkinje conduction time was significantly increased by the higher dose of dicentrine, quinidine and procainamide. 5. The ventricular repolarization time and its effective refractory period were significantly increased by the higher dose of dicentrine and the other agents. 6. The effective refractory period of the atrium, AV node and His-Purkinje system were also significantly increased by dicentrine and the other agents. 7. A voltage clamp study revealed that the prolongation of atrial action potential duration by dicentrine (9 microM) was associated with a significant inhibition of the transient potassium outward current. As well as inhibition of the transient outward current, a significant inhibition of the sodium inward current by dicentrine was found. 8.We conclude that (1) dicentrine is potentially a useful antiarrhythmic agent with type Ia and type III antiarrhythmic action; (2) the relative potency of dicentrine on the electrophysiological function of cardiac tissue is 10-20 times more than that of procainamide.

Dicentrine, an alpha-adrenoceptor antagonist with sodium and potassium channel blocking activities.[Pubmed: 7908125]

To elucidate the electrophysiological effect of dicentrine, an alkaloid isolated from Lindera megaphylla, we examined action potential and membrane currents in single cardiac cells. The tight-seal whole cell clamp technique was used. In the current clamp condition, 3 microM dicentrine prolonged rat ventricular action potential duration (APD50) from 38.9 +/- (SEM)9.8 ms to 147.8 +/- 19.7 ms (n = 12) and reduced its maximal rate of depolarization (Vmax) from 220.5 +/- 20.3 V/s to 37.0 +/- 4.0 V/s. The same concentration of quinidine increased APD50 from 42.5 +/- 5.2 ms to 182.8 +/- 15.6 ms (n = 6) and decreased the Vmax from 225.4 +/- 19.5 V/s to 32.2 +/- 3.0 V/s. Voltage clamp study revealed that dicentrine (1 to 100 microM) inhibited the integral of the transient outward current (Ito-I200) dose-dependently with a KD value of 3.0 +/- 0.5 microM. At 50 mV, the suppression of Ito by 3 microM dicentrine was accompanied by shortening of its inactivation time constant from 41.0 +/- 4.9 ms to 18.8 +/- 2.1 ms. V0.5 for the steady state inactivation curve of Ito was shifted from -25.5 +/- 2.8 mV to -40.6 +/- 2.1 mV. Compared to dicentrine, quinidine exerted stronger but the same mode of inhibition of Ito. 4-Aminopyridine, however, blocked Ito without modification of its inactivation time constant. In addition to the inhibition of Ito, the late outward current (Ilo) was significantly reduced by 10 microM each of dicentrine and quinidine to 60.0 +/- 13.3% and 37.5 +/- 6.3%, respectively. 4-Aminopyridine (2 mM) failed to inhibit this current.(ABSTRACT TRUNCATED AT 250 WORDS).

Haemodynamic effects of dicentrine, a novel alpha 1-adrenoceptor antagonist: comparison with prazosin in spontaneously hypertensive and normotensive Wistar-Kyoto rats.[Pubmed: 1356567]

1. The haemodynamic effects of dicentrine, an aporphine derivative isolated from the plant Lindera megaphylla, were investigated and compared with prazosin in rats. 2. In anaesthetized normotensive Wistar-Kyoto (WKY) rats, i.v. administration of dicentrine (0.1, 0.5, 1.0 mg kg-1) and prazosin (0.01, 0.05, 0.1 mg kg-1) induced a dose-related reduction of mean arterial pressure (MAP) which reached a maximal effect 5-10 min after injection and persisted for 2 h. 3. In anaesthetized WKY rats, a higher dose of dicentrine (1.0 mg kg-1, i.v.) did not cause any significant changes in heart rate (HR), cardiac output (CO) and stroke volume (SV) but markedly increased tail blood flow. In contrast, a higher dose of prazosin (0.1 mg kg-1, i.v.) produced a decrease in HR which paralleled the time course of the hypotensive response. 4. The hypotensive activity of dicentrine was completely abolished by alpha-adrenoceptor blockade. Both dicentrine and prazosin significantly attenuated pressor responses to noradrenaline but failed, even at maximal hypotensive doses, to impair the pressor effects of angiotensin II or vasopressin. These observations suggest that dicentrine appears to exert its hypotensive action through alpha 1-adrenoceptor blockade. 5. In conscious normotensive and spontaneously hypertensive (SH) rats, dicentrine (0.5-2.0 mg kg-1, i.v.) and prazosin (0.05-0.2 mg kg-1, i.v.) also evoked dose-related decreases in MAP which were of greater magnitude in SH rats. Oral administration of dicentrine (5 and 8 mg kg-1) to conscious SH rats caused a hypotensive effect which persisted for over 15 h.6. These results suggest that dicentrine may have therapeutic potential as an oral antihypertensive drug via alpha-adrenoceptor blockade.

Dicentrine, a novel antiplatelet agent inhibiting thromboxane formation and increasing the cyclic AMP level of rabbit platelets.[Pubmed: 1310852]

Dicentrine is an antiplatelet agent isolated from the Chinese herb Lindera megaphylla. We examined the in vitro effects of dicentrine on various aspects of platelet reactivity. Dicentrine inhibited the aggregation and ATP release of washed rabbit platelets induced by arachidonic acid (AA), collagen, ADP, platelet-activating factor (PAF), thrombin and U46619. Dicentrine also inhibited the thromboxane B2 formation caused by AA, collagen and thrombin in washed intact platelets or that induced by AA in lysed platelet homogenate, while prostaglandin D2 formation caused by AA was not increased. The generation of inositol monophosphates (in the presence of indomethacin) caused by thrombin, collagen and PAF was not suppressed significantly, nor did dicentrine suppress fibrinogen-induced aggregation of elastase-treated platelets. Dicentrine inhibited the intracellular Ca2+ increase in quin-2/AM-loaded platelets caused by thrombin, PAF, collagen and AA. The cyclic AMP level was elevated by dicentrine in a concentration-dependent manner. These data indicate that the inhibitory effect of dicentrine on platelet aggregation and ATP release was due to the inhibition of thromboxane formation and the elevation of the level of cyclic AMP.

Dicentrine, a natural vascular alpha 1-adrenoceptor antagonist, isolated from Lindera megaphylla.[Pubmed: 1686739]

1. The pharmacological activity of dicentrine, isolated from Lindera megaphylla, was determined in rat isolated thoracic aorta, guinea-pig isolated trachea and human platelet-rich plasma. 2. Dicentrine was found to be a potent alpha 1-adrenoceptor blocking agent in rat thoracic aorta as revealed by its competitive antagonism of noradrenaline- (pA2 = 8.19 +/- 0.09) or phenylephrine (pA2 = 9.01 +/- 0.10)-induced vasoconstriction. These effects still persisted in denuded aorta. It was less potent than prazosin (pA2 = 10.60 +/- 0.10), but was more potent than phentolamine (pA2 = 7.53 +/- 0.10) or yohimbine (pA2 = 6.20 +/- 0.05). 3. Inositol monophosphate formation induced by noradrenaline (3 microM) in rat thoracic aorta was suppressed by dicentrine (3-10 microM) and prazosin (3 microM). 4. A high concentration of dicentrine (30 microM) did not affect the aortic contraction induced by the thromboxane receptor agonist U-46619 (1 microM), angiotensin II (1 microM), high potassium (60 mM) or carbachol (3 microM). 5. Contraction of guinea-pig trachea caused by histamine or carbachol was slightly inhibited by dicentrine (30 microM), while beta-adrenoceptor relaxation to isoprenaline in trachea was not affected. 6. Aggregation in human platelet-rich plasma induced by adrenaline (10 microM) was blocked by yohimbine (5 microM). A high concentration of dicentrine (greater than 30 microM) caused slight inhibition of aggregation, the release reaction and thromboxane formation. Complete blockade was obtained with 150 microM dicentrine. 7. It is concluded that dicentrine is a potent, selective alpha 1-adrenoceptor antagonist in vascular smooth muscle.

Bioactive principles from the roots of Lindera megaphylla.[Pubmed: 1798790]

d-Dicentrine was isolated from the root of Lindera megaphylla. It inhibited the aggregation of washed rabbit platelets induced by ADP, collagen, arachidonic acid, and PAF. It also inhibited the high potassium- and norepinephrine-induced contraction of rat thoracic aorta. In rat ventricular cells treated with 3 microM d-dicentrine, the action potential duration (ADP50) was prolonged from 59.9 +/- 11.3 msec to 201 +/- 28.7 msec.