Joana Matos

The use of chlorophyll fluorescence for monitoring photosynthetic condition of two tank-cultivated red macroalgae using fishpond effluents

Abstract In vivo chlorophyll fluorescence measured by pulse amplitude modulated (PAM) fluorometry was used as an indicator of photosynthetic activity in tank-cultivated red algae [Gracilaria cornea and Asparagopsis armata (tetrasporophyte phase, previously known as Falkenbergia rufolanosa)] using effluent seawater from sea bream fishponds (Sparus aurata). Optimal quantum yield of indoor-grown G. cornea did not change during the period analysed (2 months). In contrast, optimal quantum yield decreased drastically in algae transferred from indoor to outdoor conditions. Maximal electron transport rate increased and photosynthetic pigments decreased in algae growing outdoors, indicating an acclimation to high irradiance. After 16 days, chlorophyll fluorescence decreased drastically and recovered partially when algae were transferred again from outdoor to indoor conditions. Falkenbergia rufolanosa was grown at three different biomass densities (4, 6 and 8 g l-1). The effects of three consecutive air compressor failure events on the photosynthetic activity were followed. An apparent degradation of the physiological conditions of the algae (resulting in their bleaching) was observed, concomitant with a strong decrease in the optimal quantum yield. This decrease was higher at algal biomass densities of 4 g l-1 than at 6 or 8 g l-1. Three days after transfer to optimal conditions, i.e., normal aeration conditions, optimal quantum yield reached values around 0.50–0.55, close to the values before stress conditions. The results revealed that the use of chlorophyll fluorescence is a powerful means to rapidly detect different stress situations in integrated cultivation of seaweeds using fishpond effluents. In particular, the optimal quantum yield of algae can be monitored regularly as an early warning of the physiological stress in cultures.

Novel potent metallocenes against liver stage malaria.

ABSTRACT Novel conjugates of the antimalarial drug primaquine (compound 1) with ferrocene, named primacenes, have been synthesized and screened for their activities against blood stage and liver stage malaria in vitro and host-vector transmission in vivo. Both transmission-blocking and blood-schizontocidal activities of the parent drug were conserved only in primacenes bearing a basic aliphatic amine group. Liver stage activity did not require this structural feature, and all metallocenes tested were comparable to or better than primaquine in this regard. Remarkably, the replacement of primaquines aliphatic chain by hexylferrocene, as in compound 7, led to a ∼45-fold-higher level activity against liver stage parasitemia than that of primaquine.

Peptidomimetic and organometallic derivatives of primaquine active against Leishmania infantum

ABSTRACT The current treatment of visceral leishmaniasis is made difficult by the low efficacy, elevated costs, low bioavailability, and high toxicity of many of the available drugs. Primaquine, an antimalarial 8-aminoquinoline, displays activity against Leishmania spp., and several of its derivatives have been developed as potential antileishmanial drugs. However, primaquine exhibits low oral bioavailability due to oxidative deamination of its aliphatic chain. We previously developed peptidomimetic and organometallic derivatives of primaquine, with higher resistance to proteolytic degradation and oxidative deamination, which presented significant activity against primaquine-sensitive pathogens such as Plasmodium or Pneumocystis. In light of these relevant findings, we decided to evaluate these compounds against both the promastigote and intramacrophagic amastigote forms of Leishmania infantum, the agent of Mediterranean visceral leishmaniasis. We found that several of these compounds had significant activity against L. infantum. One of the peptidomimetic (3c) and one of the organometallic (7a) derivatives of primaquine were active against the clinically relevant intramacrophagic amastigote form of the parasite, causing >96% reductions in the number of amastigotes per 100 macrophages at 60 and 40 μM, respectively, while being less cytotoxic for host cells than the reference drugs sitamaquine and miltefosine. Hence, compounds 3c and 7a represent new entries toward the development of new antileishmanial leads.

PRIMACENES: novel non-cytotoxic primaquine-ferrocene conjugates with anti-Pneumocystis carinii activity

Primacenes, novel ferrocene–primaquine conjugates, were synthesized and screened for their antimalarial and anti-pneumocystis activity. Primacenes obtained by coupling primaquine amino acid derivatives to ferrocenoic acid were significantly active against Pneumocystis carinii and devoid of cytotoxicity, thus being more selective than the parent drug.

Electrospray ionization-ion trap mass spectrometry study of PQAAPro and PQProAA mimetic derivatives of the antimalarial primaquine.

Electrospray ionization-ion trap mass spectrometry (ESI-MS) of imidazolidin-4-one peptidomimetic derivatives of the antimalarial drug primaquine (PQ) is reported. These compounds contain the imidazolidin-4-one moiety either at the N- or the C-terminal of a dipeptide backbone, thus respectively mimicking PQ-Amino Acid-Proline (PQAAPro) and PQProAA derivatives of PQ. Both the peptidomimetics and precursors previously developed by us are promising drug candidates, as they were found to be active against rodent Plasmodium berghei malaria and Pneumocystis carinii pneumonia. Collision-induced dissociation (CID) and tandem-mass spectra (MS) of the title compounds, and fragmentation pathways thereof, led to the following findings: (1) CID patterns present some parallelism with the reactivity towards hydrolysis previously found for the same or related compounds; (2) a positional shift of the imidazolidin-4-one ring is reflected on both degree and pathways of fragmentation, which makes tandem-MS a key tool for differentiation of imidazolidin-4-one isomers; (3) the major MS/MS fragmentation of PQProAA mimetics involves release of a neutral diketopiperazine (DKP), in parallel to the “diketopiperazine pathway” described in tandem-MS studies of oligopeptides; (4) the relative abundance of a major fragment in tandem-MS spectra is inversely correlated with the size of the N-terminal AA in PQProAA mimetics. Overall, this work embodies an original and valuable contribution towards a deeper insight into the molecular properties of novel antimalarials, which can be viewed as representative of both the 8-aminoquinoline and, especially, the imidazolidin-4-one structural classes.

Electrospray ionization mass spectrometry as a valuable tool in the characterization of novel primaquine peptidomimetic derivatives

Novel primaquine-derived antimalarials have been extensively characterized by electrospray ionization-ion trap mass spectrometry (ESI-MS). Experiments by in-source collision-induced dissociation (CID) in the nozzle–skimmer region (NSR) or by tandem mass spectrometry (MS/MS) are shown to be most valuable tools for the physico–chemical characterization of these 8-aminoquinolinic drugs that also bear the biologically relevant imidazolidin-4-one scaffold. It was possible to find parallelism between compound stability in the NSR and its reactivity towards hydrolysis at physiological pH and T. Moreover, MS/MS fragmentation patterns were characteristic for each family, providing a means for structural distinction of isomers and allowing interesting correlations to be found between the relative abundance of particular fragments and relevant structure–activity determinants, such as the Charton steric parameter, ν. In conclusion, this work provides a solid ground for establishing ESI-MS as a key tool for the physico–chemical characterization of biopharmaceuticals bearing the 8-aminoquinoline and/or the imidazolidin-4-one moieties.

Amino Acids in the Development of Prodrugs

Although drugs currently used for the various types of diseases (e.g., antiparasitic, antiviral, antibacterial, etc.) are effective, they present several undesirable pharmacological and pharmaceutical properties. Most of the drugs have low bioavailability, lack of sensitivity, and do not target only the damaged cells, thus also affecting normal cells. Moreover, there is the risk of developing resistance against drugs upon chronic treatment. Consequently, their potential clinical applications might be limited and therefore, it is mandatory to find strategies that improve those properties of therapeutic agents. The development of prodrugs using amino acids as moieties has resulted in improvements in several properties, namely increased bioavailability, decreased toxicity of the parent drug, accurate delivery to target tissues or organs, and prevention of fast metabolism. Herein, we provide an overview of models currently in use of prodrug design with amino acids. Furthermore, we review the challenges related to the permeability of poorly absorbed drugs and transport and deliver on target organs.