Isolation and structures of schleicherastatins 1-7 and schleicheols 1 and 2 from the teak forest medicinal tree Schleichera oleosa

Bioassay (P-388 lymphocytic leukemia cell line)-guided separation of an extract prepared from the bark and stem of the Sri Lankan tree Schleichera oleosa led to the isolation of seven cancer cell growth inhibitory hydroxylated sterols designated schleicherastatins 1-7 (1-7) and two related sterols, schleicheols 1 and 2 (8, 9). The structure of schleicherastatin 1 (1) was completely elucidated by X-ray crystal structure determination. Based upon that defined structure, the remaining new sterol structures were deduced by highfield (300 and 500 MHz) NMR and MS interpretations. In this new series of sterols, hydroxylation at C-22 appears to be important for promoting cancer cell growth inhibition.

Antineoplastic agents. Part 409: Isolation and structure of montanastatin from a terrestrial actinomycete

A Montana soil actinomycete, Streptomyces anulatus, produced (1 x 10(-2)% yield) a new cancer cell growth inhibitory cyclooctadepsipeptide named montanastatin (1) accompanied by the potent anticancer antibiotic valinomycin (2) in very high (5.1%) yields. Valinomycin but not montanastatin inhibited growth of a number of pathogenic bacteria and fungi. Interpretation of high-field (500 MHz) NMR and high-resolution FAB mass spectral data allowed assignment of the structure cyclo-(D-Val-L-Lac-L-Val-D-Hiv) to montanastatin. Valinomycin (2) was also isolated from actinomycetes cultured from a tree branch and animal feces collected in Malaysia. Streptomyces exfoliatus, isolated from the tree branch, was found to contain valinomycin in 1.6% yield, while the fecal isolate, S. anulatus, gave valinomycin in 0.9% yield.

Isolation and structure of the human cancer cell growth inhibitory cyclodepsipeptide dolastatin 16

An investigation of the sea hare Dolabella auricularia from Papua New Guinea has led to discovery of the new cyclodepsipeptide dolastatin 16 (3) containing two new amino acid units designated dolamethylleuine (Dml) and dolaphenvaline (Dpv). The structural elucidation was achieved by means of high-field (500 MHz) NMR and tandem MS/MS mass spectral interpretations and allowed the assignment of cyclo-(Pro-Dpv-Pro-Dml-O-Lac-Pro-O-Hiv-MeVal). The new depsipeptide exhibited strong inhibition of growth against a variety of human cancer cell lines.

Antineoplastic agents. 362. Isolation and X-ray crystal structure of dibromophakellstatin from the Indian ocean sponge Phakellia mauritiana

Bioassay-guided isolation procedures using human tumor cell lines led to isolation of dibromophakellstatin (4) from the Republic of Seychelles sponge Phakellia mauritiana. The isolation, X-ray crystal structure elucidation, absolute stereochemistry, and antineoplastic activity have been summarized. P. mauritiana was also found to contain dibromophakellin (1), debromohymenialosine (2), thymidine, deoxyuridine, and thymine.

Antineoplastic agents 338. The cancer cell growth inhibitory. Constituents of Terminalia arjuna (Combretaceae)

By means of bioassay-guided separation methods, the cancer cell growth inhibitory constituents residing in the bark, stem and leaves of the Mauritius medicinal plant Terminalia arjuna (Combretaceae) were examined. The cancer cell line active components were found to be gallic acid, ethyl gallate, and the flavone luteolin. Only gallic acid was previously known to occur in this plant. Luteolin has a well established record of inhibiting various cancer cell lines and may account for most of the rationale underlying the use of T. arjuna in traditional cancer treatments. Luteolin was also found to exhibit specific activity against the pathogenic bacterium Neisseria gonorrhoeae.

Antineoplastic agents, 325. Isolation and structure of the human cancer cell growth inhibitory cyclic octapeptides phakellistatin 10 and 11 from Phakellia sp

The two new marine sponge (Phakellia sp., western Pacific Ocean) constituents, phakellistatin 10 [1] and 11 [2], were found to be cyclic octapeptides that significantly inhibited growth of the murine P-388 lymphocytic leukemia (ED50 values of 2.1 and 0.20 micrograms/ml, respectively) and human cancer cell lines. The structures were established based on results of extensive tandem ms/ms and high-field (500-MHz) 2D 1H- and 13C-nmr analyses. All of the amino acid units (except Trp, not determined) were found to correspond to the (S)-configuration.

Antineoplastic agents, 301. An investigation of the Amaryllidaceae genus Hymenocallis

Seven species (and one cultivated variety) of Hymenocallis (Amaryllidaceae) and the related Pancratium maritima, representing a broad geographical selection, were investigated as sources of pancratistatin [1] now undergoing preclinical development as an anticancer agent. Pancratistatin [1] was found to be a constituent of H. speciosa (Singapore), H. variegated (Singapore), H. pedalis (Seychelles), H. expansa (Bermuda), H. sonoranensis (Mexico), and P. maritimum (Israel). Only two species of Hymenocallis failed to yield one or more of the related cell-growth inhibitory isocarbostyrils such as narciclasine [3a], 7-deoxynarciclasine [3b], and 7-deoxy-trans-dihydronarciclasine [2].

Antineoplastic agents, 326. The stereochemistry of bastadins 8, 10, and 12 from the Bismarck archipelago marine sponge Ianthella basta

An investigation of cancer cell-growth inhibitory constituents of the Papua New Guinea marine sponge Ianthella basta led to isolation of the C-6 hydroxybastadins 8 [1] 10 [2], and 12 [3]. The absolute stereochemistry (6S) of each bastadin (or its tetramethyl ester derivative) was determined by means of the Mosher-Trost method. Bastadins 10 [2] and 12 [3] were found to significantly inhibit the growth of a selection of human cancer cell lines. Bastadins 8, 10, and 12 inhibited growth of the Gram-positive opportunists Staphylococcus aureus and Enterococcus faecalis.

Antineoplastic agents 320: synthesis of a practical pancratistatin prodrug

Owing to its sparingly soluble properties, the potential anticancer drug pancratistatin (1) resisted conventional drug formulation procedures and the synthesis of a water-soluble prodrug became necessary. That important objective for further pre-clinical development was met by devising a route to a disodium phosphate derivative (5). The key step in the synthesis of the phenolic phosphate was phosphorylation of 1,2,3,4-tetraacetoxy-pancratistatin (2) with dibenzyloxy(N,N-diisopropylamido)-phosphine. Subsequent oxidation with m-chloroperbenzoic acid afforded phosphate 4a. Hydrogenolysis of the benzyl esters followed by base-catalysed hydrolysis of the acetate groups led to the water-soluble prodrug 5 in high yield.

Antineoplastic agents. 278. Isolation and structure of axinastatins 2 and 3 from a western Caroline Island marine sponge

The Republic of Palau marine sponge Axinella sp. was found to be an exceptionally productive source of cell growth inhibitory substances. The strongly antineoplastic polyether macrocyclic lactones halichondrin B (1) and homohalichondrin B (2) were isolated in 1.2 x 10(-6)% and 5.4 x 10(-7)% yields, respectively. In addition to axinastatin 1 (3), two new and cytostatic (GI50 values of 0.35 to 0.0072 microgram/mL against six human cancer cell lines) cycloheptapeptides designated axinastatins 2 (4) and 3 (5) were discovered in 1.4 x 10(-6)% and 1.25 x 10(-6)% yields. Structures were elucidated by high-resolution FABMS and tandem MS/MS techniques augmented by high-field (400 and 500 MHz) 2D-NMR spectral analyses. The absolute configurations were established by a combination of hydrolysis, derivatization, and chiral gas chromatographic methods.

Isolation and structure of cephalostatins 10 and 11

Further investigation of antineoplastic constituents from the marine worm Cephalodiscus gilchristi, employing a 450 kg re-collection from the Indian Ocean (Southeast Africa), has led to isolation and structural determination of two previously undetected members of the cephalostatin series, designated cephalostatins 10 [4] and 11 [5]. Structural analyses were conducted primarily employing high field 2D nmr and high resolution mass spectral techniques. All the stereochemical assignments were deduced using the original X-ray crystal structure of cephalostatin 1 and ROESY 2D nmr methods. Both cephalostatins 10 and 11 strongly inhibited growth of a series of important human cancer cell lines.

Isolation of the nickel-chlorin chelate tunichlorin from the South Pacific ocean sea hare Dolabella auricularia

The Papua New Guinea shell-less mollusc Dolabella auricularia has been found to contain a series of green to blue-green chlorins. One of these compounds was found to be the nickel chelate tunichlorin [1] which was isolated previously only from the Caribbean tunicate Trididemnum solidum. Discovery of tunichlorin [1] in a sea hare suggests that its occurrence in algae-consuming marine animals may be more common than earlier realized, and it may have a role in electron transfer or other metabolic processes.

Isolation and structure of the marine sponge cell growth inhibitory cyclic peptide phakellistatin 1

A new cell growth inhibitory (P-388 murine leukemia ED50 7.5 micrograms/ml) cycloheptapeptide designated phakellistatin 1 was isolated from two Indo-Pacific sponges, Phakellia costata and Stylotella aurantium. Structural elucidation was accomplished utilizing high field nmr, amino acid analyses, and mass spectral techniques (fab, tandem ms/ms), followed by chiral gas chromatographic procedures for absolute configuration assignments (all S-amino acid units). By these methods phakellistatin 1 [1] was found to be cyclo (Pro-Ile-Pro-Ile-Phe-Pro-Tyr), and this assignment was finally confirmed by an X-ray crystal structure determination.

Marine animal biosynthetic constituents for cancer chemotherapy

A fifteen year investigation of marine animal components as sources for new and potentially useful cancer chemotherapeutic drugs has led to our discovery of a number of such valuable substance. The especially productive Indian Ocean sea hare Dolabella auricularia has yielded (100 kg leads to or approximately 1 mg each) a series of very potent cell growth inhibitory substances designated dolastatins 1-9. The first member of this new series, dolastatin 1, may represent the most potent anticancer agent so far uncovered with, e.g., a curative response (33%) using a dose of 11 microgram/kg (T/C 240, to T/C 139 at 1.37 microgram/kg) in the National Cancer Institute's murine B16 melanoma. Structural elucidation of the new antineoplastic agents is underway, and recent progress is illustrated with peptide dolastatin 3 (P388 ED 50 2.7 x 10(-7) microgram/ml).