Melatonin had previously been shown to reduce up to four 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) cation radicals (ABTS*+) via a scavenger cascade ending with N1-acetyl-N2-formyl-5-methoxykynuramine (AFMK). However, when melatonin is added to the reaction system in much lower quantities than ABTS*+, the number of radicals scavenged per melatonin molecule is considerably higher and can attain a value of ten. Under conditions allowing for such a stoichiometry, novel products have been detected which derive from AFMK (1). These were separated by repeated chromatography and the major compounds were characterized by spectroscopic methods, such as mass spectrometry (HPLC-MS, EI-MS and ESI-HRMS), 1H nuclear magnetic resonance (NMR) and 13C NMR, heteronuclear multiple bond connectivity (HMBC) correlations. The identified substances are formed by re-cyclization and represent 3-indolinones carrying the side chain at C2; the N-formyl group can be maintained, but deformylated analogs seem to be also generated, according to MS. The primary product from AFMK (1) is N-(1-formyl-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylidenemethyl)-acetamide (2), which is obtained after purification as E- and Z-isomers (2a, 2b); a secondary product has been identified as N-(1-formyl-2-hydroxy-5-methoxy-3-oxo-2,3-dihydro-1H-indol-2-ylmethyl)-acetamide (3). When H2O2 is added to the ABTS*+ reaction mixture in quantities not already leading to substantial reduction of this radical, compound 3 is isolated as the major product, whereas 2a and 2b are virtually absent. The substances formed differ from all previously known oxidation products which derive from melatonin and are, among these, the first 3-indolinones. Moreover, the aliphatic side chain at C2 is reminiscent of other substances which have been synthesized in the search for melatonin receptor ligands.

The melatonin metabolite N1-acetyl-5-methoxykynuramine (AMK; 1), which was previously shown to be a potent radical scavenger, was oxidized using the ABTS cation radical [ABTS = 2,2'-azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid)]. Several new oxidation products were obtained, which were separated by repeated chromatography and characterized by spectroscopic methods such as mass spectrometry (ESI-MS and ESI-HRMS), 1H-NMR and 13C-NMR, HMBC, HSQC, H,H COSY correlations and IR spectroscopy. The main products were oligomers of 1 (3 dimers, 1 trimer and 2 tetramers). In all cases, the amino group N2 was involved in the reactions. Two of the dimers turned out to be cis (2a) and trans (2b) isomers containing an azo bond. In the other dimer (3a), the nitrogen atom N2 was attached to atom C5 of the second aromatic amine, with loss of the methoxy group. In the trimer (5), one N2 formed a bridge to C5 of unit B, as in the respective dimer, while this one of C had bridged to C6 of B. One of the tetramers (6) was composed of a trimer 5 attached to N2 of a fourth 1 molecule via an azo bond as in 2a/b. In the other tetramer (7), an additional C-C bond between rings B and C in 6 is assumed. Although oligomers of AMK may only attain low in vivo concentrations, the types of reactions observed shed light on the physiologically possible metabolism of AMK once reacted with a free radical. The displacement of a methoxy group, rarely seen in the oxidation of methoxylated biomolecules, underlines the reactivity of AMK (1). Preliminary data show that, in the presence of ABTS cation radicals, AMK (1) can interact with side chains of aromatic amino acids, a finding which may be crucial for understanding to date unidentified protein modification by a melatonin metabolite detected earlier in experiments with radioactively labeled melatonin.

A large number of the plants are claimed to possess the antibiotic properties in the traditional system and are also used extensively by the tribal people throughout the world. It is now mostly thought that nature has given the cure of every disease in one form or another. Plants have been known to cure people from various diseases in Ayurveda. This research focused on the screening of phytochemicals and some biological activities of Phyllanthus albizzioides. The research showed that the ethanol extracts were found to be greater chemical constituents than watery extracts. Among the chemical constituents, steroid compounds were observed in highest amount in ethanol extract and the second highest in flavonoid compounds followed by tannin compounds and pheolic compounds. Furthermore, the ethanol extracts were more effective than the watery extracts in all tested biological activities such as antioxidant, anti-diabetic, cytotoxicity, antimicrobial, antitumor and NO inhibition activities. A cyclohexanone compound was isolated from the chloroform extract of the stem bark of P. albizzioides. The relative structure was determined to be 4,5-dihydroxy-3-methyl-cyclohex-2-enone on the basic of HRESIMS, 1H NMR and 13C NMR spectroscopic analyses, including 2D NMR experiments.

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The ethanolic and acetone extracts of the whole plant of Elephantopus scaber were found to contain ethyl hexadecanoate, ethyl-9,12-octadecadienoate, ethyl-(Z)-9-octadecenoate, ethyl octadecanoate, lupeol, stigmasterol, stigmasterol glucoside, deoxyelephantopin (1) and two new germacranolide sesquiterpene lactones named 17,19-dihydrodeoxyelephantopin (2) and iso-17,19- dihydrodeoxyelephantopin (3) whose stereostructures were determined by spectroscopic methods, comparison with reported data and single-crystal X-ray analysis.