A Diterpene γ-Lactone Derivative from Pterodon polygalaeflorus Benth. as a Photosystem II Inhibitor and Uncoupler of Photosynthesis

Abstract

6α,7β-Dihydroxyvouacapan-17β-oic acid (1) was isolated from Pterodon polygalaeflorus Benth. Modification of 1 yielded 6α-hydroxyvouacapan-7β,17β-lactone (2) and then 6-oxovouacapan- 7β,17β-lactone (3). Photosynthesis inhibition by 3 was evaluated in spinach chloroplasts. The uncoupled non-cyclic electron transport rate and ATP synthesis were inhibited by 3, which behaved as a Hill reaction inhibitor. Furthermore, 3 acted as an uncoupler because it enhanced the basal and phosphorylating electron transport rate on thylakoids. This last property of 3 was corroborated when it was observed that it enhances the Mg2+-ATPase activity. In contrast, 3 did not affect photosystem I (PSI) activity. Analysis of the partial photosystem II (PSII) reactions from water to DCPIPox and water to silicomolybdate allowed to locate the inhibition sites at the redox components of PSII. The OJIP test of the chlorophyll a fluorescence transient confirmed that the inhibition sites were 1.) the oxygen-evolving complex (OEC) and 2.) by the formation of silent centers in the non-QA reducing centers.

Theoretical and experimental NMR studies of the Swern oxidation of methyl 6α,7β-dihydroxyvouacapan-17β-oate

“…IR (KBr) m max /cm -1 3500, 2980, 2820, 1750, 1720, 1460, 1420, 1390, 1260, 1130, 1050, and 760. NMR data of 4 are in agreement with the literature[8,27]. Methyl 6a-hydroxy-7-oxovouacapan-17b-oate(5): 1 H NMR (400 MHz; CDCl 3 ) d H 7.24 (m; H-16), 6.29 (d, J = 1.2 Hz; H-15), 4.48 (dd, J = 12.7 and 3.9 Hz; H-6), 3.93-3.85 (m; H-14), 3.79 (s; OCH 3 ), 3.66 (d, J = 3.9 Hz; OH), 3.19 (dd, J = 12.2 and 10.2 Hz; H-9), 2.74 (dd, J = 16.1 and 4.7 Hz; H-11a), 2.63-2.50 (m; H-11b), 1.80-1.70 (m; H-8), 1.70-1.50 (m; H-2a and H-2b), 1.60-1.40 (m; H-3a), 1.30-1.15 (m; H-3b), 1.29 (s; H-20), 1.27-1.20 (m; H-1b), 1.23 (d, J = 12.7 Hz; H-5), 1.17 (s; H-19), 1.15 (s; H-18), and 1.13-1.00 (m; H-1a).…”

“…Analgesic and anti-inflammatory activities have been observed for compound 1 [9][10][11]. The relationships between the chemical structure and the biologic activities of 1 and its derivative lactones [12][13][14][15], Mannich bases [15,16], amides [17][18][19], carbamates [20], and other compounds [21][22][23][24][25][26][27] have been investigated. These derivatives show anti-inflammatory, analgesic, sedative, anticonvulsant, and plant growth regulatory activities.…”

Evaluation of Alkaloids Isolated from Ruta graveolens as Photosynthesis Inhibitors

“…The transient bands show exactly this effect ( Figure 4 A,B). Phase I appears when a dynamic equilibrium is reached between the reduction of the plastoquinone pool by the electron flow from the PSII and its oxidation due to PSI activity [ 22 ].…”

“…Intact chloroplasts were isolated from spinach leaves ( Spinacea oleracea L.), as previously described [ 12 , 22 , 25 ]. Chlorophyll concentration was measured spectrophotometrically through a chloroplast suspension in a solution of 400 mM sucrose, 5 mM MgCl, 10 mM KCl, 30 mM tricine-KOH, and pH 8.0 [ 12 ].…”

Sesquiterpenes from Celastrus vulcanicola as Photosynthetic Inhibitors

“…Basal electron transport was determined by illuminating chloroplasts (20 µg chlorophyll per mL) during 1 min in the basal electron transport medium (3 mL). 21 Photophosphorylating noncyclic electron transport was measured as basal noncyclic electron transport except that 1 mM ADP and 3 mM Pi were added. Uncoupled electron transport was tested in the basal electron transport; medium and 6 mM NH4Cl were added as uncoupler.…”